JPH05287347A - Carbonaceous material injection method for suppressing slag foaming - Google Patents

Abstract

(57) [Summary] [Object] The present invention is intended to suppress slag foaming in a hot metal pretreatment process in which lime, scale, and other refining agents are added to hot metal to desiliconize, dephosphorize, or desulfurize desulfurize hot metal. Carbon material injection method. [Composition] In the hot metal pretreatment method in which lime, scale, and other refining agents are added to hot metal to perform desiliconization, dephosphorization, or dephosphorization desulfurization of hot metal, the slag foaming height is maintained within the range of the container height. As described above, in the hot metal pretreatment method for controlling the slag foaming height by adding the carbonaceous material at a rate of 0.1 kg or more and less than 0.8 kg per ton of hot metal and a blowing rate of 5 to 100 kg / min per one suppressing operation. A carbonaceous material blowing method for suppressing slag foaming, characterized in that a carbonaceous material having a particle diameter of 0.1 to 1 mm and a carbonaceous material having a particle diameter of 1 to 5 mm are added respectively by independent blowing systems.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to hot metal such as lime, scale,
The present invention relates to a carbonaceous material blowing method for suppressing slag foaming in a hot metal pretreatment step of performing desiliconization, dephosphorization or dephosphorization desulfurization of hot metal by adding other refining agents.

[0002]

2. Description of the Related Art When refining steel by decarburizing hot metal by blowing or blowing high-pressure oxygen in a converter, not only decarburization but also dephosphorization according to the target composition of steel is performed in the converter. In order to carry out desulfurization, it is usually necessary to add lime and other refining agents. In this case, it is necessary to add a large amount of lime in order to change the slag containing SiO ₂ as a main component, which is generated by the desiliconization reaction at the initial stage of blowing in the converter, into a slag having a high basicity. In recent years, in order to reduce the amount of lime used and economically perform dephosphorization and desulfurization, a so-called hot metal pretreatment method in which hot metal is previously subjected to desiliconization, dephosphorization, and desulfurization in another container has been widely performed. In this case, as a container for hot metal pretreatment, a hot metal carrier container such as a speeded car or a hot metal ladle is used.
Since these vessels are not originally refining vessels, the freeboard is small, and slag foams during desiliconization, dephosphorization, and desulfurization, and slag often flows out of the reaction vessel.

As a countermeasure against such slag outflow, conventionally, mainly two methods have been taken. The first is a method in which, once the slag outflow from the refining container begins, the blowing of the refining agent is suspended until the slag outflow stops. The second method is a method in which a pit for the outflow slag is dug around the hot metal pretreatment container and the outflow slag is carried out after the treatment so that the refining work is not hindered even if the slag flows out. These methods have the following problems. First of all, in the case of the first method of interrupting the blowing of the refining agent, the interruption of the treatment leads to the extension of the treatment time, which not only becomes a factor inhibiting the operation of the converter which is a post-process, but also has a large adverse effect of lowering the temperature, Regarding the second method, the slag outflow usually contains 10% or more of iron, so not only the iron yield will deteriorate unless iron in the slag is recovered, but also because pits are arranged. It is not economical because it requires new work such as the equipment cost and carrying out slag in the pit.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and effectively suppresses the foaming of slag, which is the root cause of the conventional problems, to prevent slag outflow, which is economical. The purpose is to perform hot metal pretreatment.

[0005]

According to the present invention, the foaming of the slag is caused by the expansion of the volume of the slag by the CO gas bubbles generated during the desiliconization, dephosphorization and desulfurization treatments, and the foaming height is It is dominated by the stability of the slag liquid film between bubbles, and carbon material, which is a substance that is difficult to get wet with the slag, is added, and the slag liquid film between the bubbles is destroyed, and foaming is promoted by promoting coalescence and rupture of bubbles. The present invention was made based on the findings of the present inventors that the height is reduced, and the gist thereof is as follows. In the hot metal pretreatment method in which lime, scale, and other refining agents are added to hot metal to perform desiliconization, dephosphorization, or dephosphorization desulfurization of hot metal, so that the slag foaming height is maintained within the range of the container height , 0.1% per ton of hot metal per suppression work
It is a hot metal pretreatment method for controlling the slag foaming height by adding at least 1 kg and less than 0.8 kg, and the particle size is 0.1 to 1 mm.
The carbonaceous material of No. 1 and the carbonaceous material of 1 to 5 mm are respectively added by independent blowing systems, and the forming is suppressed promptly and for a long time after the addition of the carbonaceous material.

The present invention will be described in more detail below. First, the steps to which the present invention is applied will be described. The process to which the present invention is applied is a hot metal pretreatment process in which lime, scale and other refining agents are added to hot metal to desiliconize, dephosphorize and desulfurize the hot metal. As a refining vessel for performing hot metal pretreatment, a tope car or a hot metal ladle is usually used.However, if slag outflow or bubbling height is a problem, it may be a reactor or other reaction vessel. Absent.
Further, as the refining agent, lime and scale are usually mainly used, but it goes without saying that the present invention can be applied to other refining agents such as sodium carbonate. The slag outflow during hot metal pretreatment is particularly problematic in the refining process for the purpose of dephosphorization and desulfurization.However, even if refining for other purposes such as desiliconization before dephosphorization, slag outflow The application of the present invention is effective as long as the foam height is a problem. That is, the present invention can be applied to any hot metal pretreatment process that requires controlling the foaming height of the refining slag.

The most important work in applying the present invention is
When the slag foaming height was monitored and it was determined that the foaming height reached the outflow height, the particle diameter of 0.
0.1 to 1 mm of coke powder and 1 to 5 mm of coke powder with a particle diameter of 1 to 5 mm per ton of hot metal
The point is to add at least g and less than 0.8 kg, and repeat this operation as necessary. Regarding the effect of the carbonaceous material particle size on the suppression of forming, as shown in FIGS. 2 and 3, when the particle size is small even if the addition amount is the same, the time from the start of the carbonaceous material addition until the suppression effect appears is short. It was also found that when the duration of the suppression effect is short, on the other hand, when the particle size is large, the time from the start of addition of carbonaceous material to the appearance of the suppression effect is long, but the duration of the suppression effect is long. Therefore, in order to suppress the forming immediately after the addition of the carbonaceous material and to maintain the carbonaceous material, it is necessary that the carbonaceous material to be added has a wide particle diameter distribution in the coarse particles and the fine particles. In order to stably blow the carbonaceous material into the forming slag, it is desirable that the carbonaceous material of 0.1 to 1 mm and the carbonaceous material of 1 to 5 mm prepared in advance be uniformly added.

Considering the time margin from the start of the addition of the carbonaceous material to the appearance of the suppression effect, the foaming height at which the addition of the carbonaceous material should be added should be added at the latest when it reaches 0.3 m below the furnace mouth. It is desirable to start. Although coke powder is most effective as the foaming inhibitor to be added, coal may be used instead of coke powder, or a mixture of coke powder and other powders such as calcium carbonate may be used depending on the purpose. Even in that case, by adding 0.1 kg or more of the total amount of carbon components in the powder to be added per ton of hot metal, the same effect as adding only the coke powder can be obtained.

As shown in FIG. 2, the amount of coke powder added is preferably 0.1 kg or more per ton of hot metal, and the larger the amount of coke powder added, the longer the duration of the foaming suppression effect is, which is preferable. Not only is it economical not to increase, but as shown in FIG. 4, the added coke reduces FeO in the slag, which causes adverse effects such as a decrease in dephosphorization oxygen efficiency. The upper limit is less than 0.8 kg per unit. On the other hand, if the addition amount is less than 0.1 kg per ton of hot metal, it may not be possible to suppress slag outflow even if coke is added, which is not preferable. In addition, when adding the suppressor, it is desirable that the suppressor is continuously blown instead of being added all at once so as to be uniformly blown into the slag.

At this time, it should be noted that the forming suppression degree changes depending on the addition rate of the carbonaceous material.
According to the results of the suppression experiment using the tope car of the present inventors, when the carbonaceous material addition rate is less than 5 kg / min, it is impossible to suppress the forming even if the carbonaceous material is added. It was not possible to prevent the outflow of slag into. Similarly, the carbonaceous material addition rate is 100 kg.
If the flow rate is changed to / min, the temperature of the exhaust gas rises and the dust collection efficiency decreases due to the increase in the heat load of the dust collector and the heat deformation cracks in the dust collection duct cause troubles in operation. Therefore, it is desirable that the upper limit of the amount of carbon material added be 100 kg / min.

Further, if the particle size on the coarse particle side is too large, it becomes difficult to continuously supply the powder by, for example, pressure feeding of a pipe. As mentioned above, it is desirable to add the forming inhibitor such as coke to the minimum necessary from the viewpoint of economic efficiency and avoiding adverse effects on dephosphorization.Therefore, the amount of coke powder added per slag outflow suppression operation should be adjusted. By restricting as described above and repeating this work as necessary, it becomes possible to suppress slag foaming. In the present invention, when the particle size on the fine grain side is too small, there is also a problem that the powder is scattered and a loss of the powder occurs, but the condition that the powder is reliably added to the foaming slag is secured, It is not necessary to specify the lower limit of the particle size if the manufacturing cost can be ignored. However, from the viewpoint of manufacturing cost, it is practically desirable that the thickness be 0.1 mm or more.

The method of adding the coke powder is most preferably a method in which the carrier gas such as nitrogen gas is blown into the slag from the lance to blow it into the slag. It does not matter if it is other than the blowing method. According to the experiments conducted by the present inventors, the foaming suppressing effect is not sufficient by simply adding the bag-filled carbonaceous material from above, and in order to reliably disperse the powder in the slag, it is necessary to measure 500 mm from the hot metal surface. From 2
It is desirable to surely blow the coke powder into the upper layer of the foaming slag below the surface of the foaming slag at the position of 000 mm.

[0013]

EXAMPLES The effects of the present invention will be described below based on examples. FIG. 1 shows a schematic view of an embodiment of hot metal treatment to which the present invention is applied. In the hot metal pretreatment shown in FIG. 1, coke having a particle diameter of 0.1 to 1 mm and coke having a particle diameter of 1 to 5 mm were blown into the forming slag by independent blowing systems to suppress foaming of the slag. The amount of carbonaceous material added, the time when the suppression effect appears, and the suppression duration,
The results are shown in FIGS. 2 and 3 in comparison with the case of the conventional powder coke. As is clear from FIGS. 2 and 3, it was found that by using coke powder having different particle size distributions of coarse particles and fine particles, it is possible to suppress foaming of slag with immediate effect and sustainability. It was As a method of adding the carbonaceous material, in addition to the exclusive blowing lance 8 shown in FIG. 1, the same effect can be obtained by the method of FIGS. 5 and 6 in which the carbonaceous material blowing hole is provided in the refining agent blowing lance 5. Be expected.

[0014]

From the above Examples and Comparative Examples, according to the method of the present invention, it is possible to effectively carry out the refining reaction in the hot metal pretreatment, and as a result, the slag outflow occurs due to the increase in the slag foaming height. It became possible to carry out operations smoothly in a short time without incident.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing the effect of the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an effect of another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the relationship between the amount of coke added and the dephosphorization efficiency index.

FIG. 5 is an explanatory diagram showing another embodiment of the present invention.

FIG. 6 is an explanatory diagram showing still another embodiment of the present invention.

[Explanation of symbols]

 1 Mixing pig car 2 Pressure feed tank 3 Pressure feed pipe 4 Weigher 5 Refining agent blowing lance 6 Input port 7 Carbon material storage hopper 8 Carbon material blowing lance 9 Pressure feeding gas supply source 10 Refining agent addition hopper 11 Carbon material 12 Slag 13 Slag 14 Charcoal material addition hole 15 Carbon material injection control device 16 Slag height measuring device 17 Slance height measuring lance 18 Inert gas discharge hole

Claims (1)

[Claims] 1. In a hot metal pretreatment method in which lime, scale, or other refining agent is added to hot metal to perform desiliconization, dephosphorization or dephosphorization desulfurization of hot metal, the slag foaming height falls within the range of the container height. In order to maintain the temperature, the carbonaceous material is added at a rate of 0.1 kg or more and less than 0.8 kg per ton of hot metal per one ton of suppression work at a blowing rate of 5 to 100 kg / min to control the slag foaming height. In the method, a carbonaceous material having a particle diameter of 0.1 to 1 mm and a carbonaceous material having a particle diameter of 1 to 5 mm are added by independent injection systems, respectively, to prevent slag foaming.