JPH05156338A - Method for reusing low phosphorus converter slag - Google Patents

Abstract

PURPOSE:To reduce consumption and loss quantity of fluorite at the time of using low P converter slag as slag-making agent in a dephosphorizing furnace. CONSTITUTION:At the time of reusing the low P converter slag 5 obtd. at the time of decarbonize-refining molten iron already executing the dephosphorized treatment in the converter 2 and receiving the converter slag 5 removed from the converter 2 into a slag pan 3, in the condition of pre-charging auxiliary material of at least the fluorite 4, etc., in the slag pan 3, the above converter slag 5 is received, and after the above auxiliary material 4 is melted and mixed in the converter slag 5, this auxiliary material is used to the dephosphorizing treatment in the dephosphorizing furnace 1 or a ladle 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reusing a low-P converter slag obtained when converter hot smelting of dephosphorized hot metal is performed.

[0002]

2. Description of the Related Art In recent years, in converter decarburization refining, due to the lower content of phosphorus or sulfur, prior to the converter decarburization refining,
A dephosphorization pretreatment is carried out in the hot metal stage. Due to the spread of this hot metal preliminary dephosphorization process, converter slag generated during converter refining has a very low phosphorus content and contains a large amount of quicklime, etc. It is reused as a slag.

For example, in Japanese Patent Application No. 1-18193 and Japanese Patent Application No. 1-250939, two converters consisting of a dephosphorization furnace 1 and a decarburization furnace 2 are used as shown in FIG. In the preliminary dephosphorization → decarburization process, the converter slag generated in the decarburization furnace 2 is used again as a slag-forming agent for the dephosphorization treatment in the dephosphorization furnace 1.

At the time of dephosphorization in the dephosphorization furnace 1, since oxygen blowing is carried out under the temperature condition of a relatively low temperature range of 1300 to 1350 ° C. which is advantageous for dephosphorization, slag formation of the solvent medium is carried out. However, since a large amount of fluorspar is added, refining was performed while maintaining the F (fluorine) concentration in the slag at about 10% or more.

[0005]

However, when a large amount of fluorspar is put into the dephosphorization furnace 1, a part of the fluorspar is lost from the furnace opening before it is melted, and the fluorspar is introduced into the dust removal process together with the converter exhaust gas. Get burned.

[0006] In the dust removing process, dust is removed by spray injection or the like, but fluorine in the fluorite component is dissolved and becomes water having a high fluorine concentration and flows out. Water having a high fluorine content is highly corrosive to metals and promotes corrosion of pipes for dust removal systems or exhaust gas treatment systems, which is a great management problem and is not preferable from an environmental standpoint. In addition, since fluorspar has been depleted in terms of resources, it is desirable to save energy when using it.

Therefore, the main object of the present invention is to reduce the amount of fluorspar used and the amount of loss thereof when utilizing the low P converter slag as a slag-forming agent in a dephosphorization furnace, and to corrode dust-removing system pipes. , To prevent environmental pollution.

[0008]

[Means for Solving the Problems] The above-mentioned problems are obtained when the dephosphorization-treated hot metal is decarburized and refined in a converter.
When the converter slag is reused as the slag-forming agent in the dephosphorization treatment, when the converter slag discharged from the converter is received in the slag pan, the slag pan contains at least fluorite in advance. The problem can be solved by receiving the converter slag in a state where one or more auxiliary materials are charged, melting and mixing the auxiliary material in the converter slag, and then performing the dephosphorization treatment.

When the low P converter slag is reused in the converter dephosphorization treatment, the converter slag is received with the fluorspar being charged in the slag pan, and the basicity is 2 to 4 and fluorine is used. Concentration 10 to 20%, T. in slag. When adjusting the Fe content to 5 to 15% and reusing it for the dephosphorization treatment of the ladle, the slag pan is charged with fluorspar and iron oxide, and the converter slag is received and the basicity is 2 to 4 , Fluorine concentration 10 to 20%, T. in slag. Fe is preferably adjusted to 25 to 35%.

[0010]

In the conventional method shown in FIG. 3, the low P converter slag obtained by the converter decarburization was directly charged into the dephosphorization furnace, and the fluorspar was separately charged into the furnace separately. , Some of the fluorite was lost from the furnace mouth. In the present invention, when the converter slag is taken out from the converter, the slag is received while the slag pan is already charged with the slag, so that the slag is melted and mixed into the converter slag.

Therefore, when it is put into the dephosphorization furnace, it can be efficiently dissolved together with the converter slag without being lost outside the furnace, so that the amount of fluorspar used can be greatly reduced and the fluorine content outside the furnace can be greatly reduced. Will not be discharged, thus preventing corrosion of dust-removal piping and environmental pollution.

[0012]

EXAMPLES The present invention will be described in detail below based on examples. Based on FIG. 1, a converter refining process according to the method of the present invention will be described. Reference numeral 1 denotes a dephosphorization furnace using a converter, and the hot metal tapped from the blast furnace is subjected to dephosphorization processing in the dephosphorization furnace 1 as a hot metal preliminary treatment. In the preliminary dephosphorization treatment, a low P converter slag according to the present invention, which will be described later, is used as a slag material, and the dephosphorization conditions are, for example, a top-bottom blowing converter and top blowing O.
₂ amount 1.0 to 1.4 Nm ³ /min.t, bottom blowing inert gas amount 0.08 to 0.15 Nm ³ /min.t, blowing temperature 130
The dephosphorization treatment is performed under the condition of 0 to 1350 ° C.

The hot metal that has been subjected to the hot metal preliminary treatment (dephosphorization treatment) is decarburized in the converter 2. At the time of decarburizing treatment, a solvent medium such as quick lime, limestone, dolomite, fluorite, iron oxide or the like is added, and the decarburizing treatment is carried out under appropriate blowing conditions until the component range is adjusted according to the purpose.

After the decarburizing treatment is completed, the molten steel 6 is sent to a process such as tapping and ingot casting or continuous casting. On the other hand, as for the converter slag 5, as shown in FIG. 2, the slag pan 3 is loaded with one or more auxiliary materials containing the fluorspar 4 and is received into the converter slag 5. The auxiliary material 4 is uniformly melted and mixed. Due to safety concerns, the converter slag 5 that has been received is once cooled and then used as a slag material in the dephosphorization process by the dephosphorization furnace 1 or the ladle 6.

When the low-P converter slag 5 is reused for preliminary dephosphorization treatment in the dephosphorization furnace 1, it is preferable that the basicity is 2 to
4, fluorine concentration 10 to 20%, T. Fe5-1
It is adjusted to be 5%. When the basicity is less than 2, the P removal capacity is low, and it is necessary to add quick lime.
If it exceeds, the degree of basicity is high and slag formation is poor. Further, when the fluorine concentration is less than 10%, the slag melting point is high, resulting in poor slag formation, and when it exceeds 20%, the furnace condition is deteriorated and the dust removal system is corroded due to the lost firefly. T. in slag F
If e is less than 5%, the progress of slag formation in the converter slag is delayed.

In the case of reuse in the ladle dephosphorization treatment, preferably, the converter slag 5 is loaded with the fluorspar and iron oxide charged in the slag pan, and the basicity is 2 to 4 , Fluorine concentration 10 to 20%, T. in slag. Fe is preferably adjusted to 25 to 35%. In the preliminary dephosphorization with the ladle 6, iron oxide is added to the T. This is for increasing Fe. When Fe is less than 25%, the degree of oxidation is low, resulting in poor P removal. When it exceeds 35%, the content of quicklime is low, resulting in poor P removal.

(Embodiments) The effects of the present invention will be clarified below with reference to embodiments. In the hot metal pretreatment in the upper-bottom blowing converter, dephosphorization treatment was performed by the method of the present invention and the conventional method, and the amounts of fluorite used and the fluorine concentration of the dust removal water were compared. The results are shown in Table 1. The dephosphorization treatment conditions and the like were set to the values shown in Table 1.

[0018]

[Table 1]

As is clear from Table 1, according to the method of the present invention, the amount of fluorspar used can be reduced to about 1/5 to 1/10 as compared with the conventional method. Further, the fluorine concentration of the dust removal water could be reduced to about 1/6 as compared with the conventional method.

[0020]

As described above in detail, according to the present invention, when the low P converter slag is used as a slag-forming agent in the dephosphorization furnace, the amount of fluorite used and the amount lost are reduced, and the dust removal system is reduced. It is possible to prevent corrosion of pipes and the like and environmental pollution.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a refining process according to the method of the present invention.

FIG. 2 is a diagram showing a procedure for receiving a converter slag according to the present invention.

FIG. 3 is a schematic diagram of a conventional refining process.

[Explanation of symbols]

1 ... Dephosphorization furnace, 2 ... Decarburization furnace, 3 ... Slag pan, 4 ... Fluorite, 5
… Converter slag, 6… ladle

Claims (3)

[Claims] 1. A low P converter slag, which is obtained when dephosphorizing hot metal is decarburized and refined in a converter, is reused as a slag-forming agent in the dephosphorization process. When receiving the converter slag that is discharged from the slag pan with the slag pan, the converter slag is received while the slag pan is charged with at least one auxiliary material containing at least fluorspar, and the auxiliary material is A method for reusing a low-P converter slag, which comprises melting and mixing the slag in a converter slag, and then subjecting the mixture to the dephosphorization treatment. 2. A converter slag is received in a state where fluorspar is charged in a slag pan, basicity 2 to 4, fluorine concentration 10 to 20%, and T. The method for reusing a low-P converter slag according to claim 1, which is subjected to converter dephosphorization treatment after adjusting to 5 to 15% Fe. 3. A converter slag is received with fluorspar and iron oxide charged in a slag pan, with a basicity of 2 to 4 and a fluorine concentration of 10
~ 20%, T. in slag. The method for reusing a low-P converter slag according to claim 1, wherein the method is subjected to ladle dephosphorization treatment after adjusting to 25 to 35% Fe.