KR20040032522A - Method for Pre-Treating Pig Iron - Google Patents

Abstract

PURPOSE: A hot metal pretreating method is provided which obtains superior pretreatment effect of hot metal by injecting ladle slag into hot metal as flux during pretreatment of hot metal and recycles steelmaking byproduct disused by using the ladle slag generated as a byproduct from the steelmaking process. CONSTITUTION: In a method for pretreating hot metal by injecting sintered ore into a reaction container containing hot metal at a time point corresponding to less than 20% of the total pretreatment time and injecting quicklime (CaO) into hot metal during pretreatment, the hot metal pretreating method is characterized in that ladle slag containing 35 to 45 wt.% of CaO, 5 to 15 wt.% of SiO2 and 20 to 35 wt.% of Al2O3 is injected into the reaction container at the time point corresponding to less than 20% of the total pretreatment time so that basicity (CaO/SiO2) of slag produced on the hot metal becomes 1.2 to 1.7, wherein an injection quantity of the ladle slag satisfies a value determined by the following mathematical expression 1: injection quantity of ladle slag(kg)={hot metal quantity(ton)xhot metal£Si|(wt.%)x3-CaO injection quantity(kg)}x4.

Description

Method for Pre-Treating Pig Iron}

The present invention relates to a molten iron preliminary treatment method for removing the silicon, phosphorus, sulfur, etc. contained in the molten iron from the blast furnace, and more particularly to a method of preliminary molten iron using a ladle slag which is a by-product of steelmaking. It is about.

The molten iron pretreatment process usually includes (furnished) molten iron from the blast furnace in an open ladle, which is a reaction and transport container, and then sintered ore and, if necessary, fluorite, are injected into the molten iron by injection method. Quicklime powder and other fluxes, if necessary, are blown out to carry out desilification and demineralization.

The desulfurization reaction, the dephosphorization reaction and the deflow reaction are shown in the following reaction formulas (1), (2) and (3), respectively.

Si + 2FeO = SiO ₂ + 2Fe

2P + 5FeO = P ₂ O ₅ + 5Fe

CaO + S = CaS + O

In the conventional method, when the molten iron drawn from the blast furnace arrives in the open ladle and arrives at the preliminary treatment process, a sintered ore is first introduced into the open ladle to induce a desulfurization reaction such as the reaction formula (1).

This is because silicon contained in the molten iron has a strong affinity with oxygen, and it is possible to remove this silicon component so that the subsequent work of Tallinn is possible.

However, when the sintered ore is added to the upper portion as in the conventional method, the silicate (SiO ₂ ; silicate) generated during the de-silification operation rises to the molten iron surface and aggregates to form a slag layer.

At this time, the slag layer formed is mostly composed of silica, and due to the high viscosity (viscocity) characteristic of the silicon oxide tends to prevent the carbon monoxide gas generated as shown in the following reaction formula (4) to escape.

C + FeO = CO + Fe

Therefore, the slag layer easily swells during desulfurization, and the slag overflows in open ladles, which are a limited volume of reaction vessels.

At this time, the slag was discharged to the outside of the open ladle and flowed out of the unreacted sintered luminosity container, which lowered the reaction efficiency. There was a problem polluting the environment

Meanwhile, the technology of using the steelmaking by-product generated in the steelmaking process in the steelmaking process has been mainly applied to converter refining and secondary refining processes.

As an example, a direct recycling technology of liquid ladle slag (Korean Patent Application No. 1994-29054) is known. Here, the liquid ladle slag is charged into a converter and recycled as an auxiliary material for converter refining.

As another example, a chartering desulfurization method using converter slag (Korean Patent Application No. 2000-56887) is known, in which the converter slag is used as a direct desulfurization agent to recover valuable metals in the charter preliminary treatment for the desulfurization of the charter. The main purpose is to.

That is, in this case, slag is used in the pretreatment process, but converter slag is used and it is used as a direct desulfurization agent.

The present invention has been proposed to solve the above-mentioned problems of the prior art, and when the preliminary treatment of molten iron is added to the ladle slag as a flux to lower the viscosity of the slag can be obtained not only excellent pretreatment effect of molten iron but also steelmaking It is an object of the present invention to provide a method for preliminary treatment of molten iron to recycle steelmaking by-products that are discarded by using ladle slag generated as a by-product from the process.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention relates to a method of pretreatment of molten iron by adding sintered ore at a time point of not more than 20% of the total pretreatment time in the reaction vessel in which the molten iron is repaired, and adding quicklime (CaO) during the preliminary treatment.

At 20% of the total pretreatment time, ladle slag, a steelmaking by-product, is added to the reaction vessel so that the basicity (Ca0 / SiO ₂ ) of slag generated on the molten iron is 1.2 to 1.7, and the molten iron is pretreated. It is about how to.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention relates to a molten iron preliminary treatment method that can more efficiently remove silicon, phosphorus, sulfur, etc. by using the ladle slag as a steelmaking by-product during molten iron preliminary treatment.

That is, the present invention, by putting the ladle slag generated as a by-product from the steelmaking process during the molten iron preliminary treatment in the reaction vessel where the molten iron is repaired, the liquid slag is easily formed on the molten iron surface and lower the viscosity of the slag, and the pretreatment process Carbon monoxide gas generated in the air is easily discharged to further improve the efficiency of the charter preliminary treatment reaction.

In the present invention, a sintered ore is added to the reaction vessel in which the molten iron is repaired at a time of 20% or less of the total pretreatment time, and calcined preliminary to remove silicon, phosphorus and sulfur in the molten iron by adding quicklime (CaO) during the preliminary treatment. Applies to treatment method.

Usually, the amount of sintered ore input during the molten iron preliminary treatment is about 35-60kg / ton-pig, the amount of quicklime (CaO) is about 35-50kg / ton-pig, and if necessary, 0.5-2.0kg / ton-pig Fluorite may be added.

The quicklime is supplied into the molten steel in the form of powder by the injection method, and the supply is usually performed from the start of pretreatment to the end.

When fluorspar is charged, the loading is usually done at 60-70% of the total pretreatment time.

In the present invention, as the ladle slag added by the flux, it is preferable to use those containing CaO: 35 to 45% by weight, SiO ₂ : 5 to 15% by weight, and Al ₂ O ₃ : 20 to 35% by weight. .

The input amount of the ladle slag is determined by the molten iron component and the molten iron content, and is set so that the basicity (Ca0 / SiO ₂ ) of the slag generated on the molten iron becomes 1.2 to 1.7.

Preferably ladle slag is added so that the basicity (Ca0 / SiO ₂ ) of the slag is 1.5.

A more preferable amount of ladle slag is set to a value determined by the following equation (1) while the slag basicity (Ca0 / SiO ₂ ) is 1.2 to 1.7.

(Equation 1)

Ladle slag dose (kg) = {melt dose (ton) x molten iron [Si] (wt%) × 3-CaO dose (kg)} × 4

In the present invention, the ladle slag is added at a time point within 20% of the total pretreatment time.

The reason why the ladle slag is added as a flux and the feeding time is within 20% of the total pretreatment time is because the viscosity of the silica may be reacted with the silica formed during the desulfurization work occurring at the beginning of the preliminary treatment process. This is to lower the viscosity of the whole slag.

When ladle slag is added so that the slag basicity (Ca0 / SiO ₂ ) is less than 1.2 or exceeds 1.7, the viscosity of the slag becomes large, so the amount of ladle slag added is the basicity of slag ( Ca0 / SiO ₂ ) is set to 1.2-1.7.

The size of the ladle slag is preferably to be 100mm or less in diameter, because the melting of the ladle slag does not occur easily.

And when the size of the ladle slag is too small because it is discharged out of the container by a dust collector or the like, in consideration of this point it is preferable that the size of the ladle slag is 5mm or more.

As described above, when the ladle slag is added according to the present invention, the input amount of the sintered ore is less than 10 kg / ton-pig and the production ash is less than 3 kg / ton-pig than the conventional method. Can be achieved.

Moreover, according to the present invention, even if fluorite is added according to the conventional method, it is not necessary to add fluorite.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example)

In the process of preliminary treatment of the molten iron by adding the powdered CaO and sintered ore as shown in Table 1 to the molten iron having a composition as shown in Table 1, ladle slag having the composition of Table 2 is added to the molten iron in Table 1 After the pretreatment, the content of Si, P, and S in the molten iron and the dephosphorization rate were investigated, and the results are shown in Table 3 below.

Example No. Tonnage CaO powder (kg) Sintered ore (kg) Ladle Slag (kg) Si, P, S content in molten iron before pretreatment Si (% by weight) P (wt%) S (% by weight) Inventive Example One 83 1530 4600 747 0.24 0.091 0.035 2 83 2000 4900 965 0.31 0.099 0.024 3 75 2200 4500 899 0.37 0.103 0.031 4 85 2400 5000 2004 0.61 0.108 0.021 5 82 2300 4100 1333 0.44 0.105 0.019 6 76 2500 3500 830 0.33 0.105 0.018 7 75 2600 3900 947 0.39 0.11 0.02 8 75 2600 4900 1117 0.46 0.106 0.014 9 82 2600 3700 999 0.33 0.109 0.016 10 75 2600 4000 923 0.38 0.103 0.018 11 78 2600 4500 1262 0.47 0.107 0.016 12 71 2600 3800 772 0.37 0.11 0.014 13 67 2600 3900 697 0.4 0.108 0.017 Conventional example One 75 2200 4200 0 0.4 0.104 0.019 2 83 2200 4500 0 0.38 0.102 0.023 3 65 2200 3500 0 0.28 0.105 0.021

Composition of Ladle Slag (% by weight) T. Fe CaO SiO ₂ Al ₂ O ₃ MgO MnO TiO ₂ P ₂ O ₅ 7.5 41.0 11.4 25.4 6.5 2.7 0.74 0.48

Example No. Content of Si, P, S in molten iron after pretreatment (% by weight) CaO / SiO ₂ Tallinn (%) Si P S Inventive Example One 0.02 0.018 0.023 1.61 80.2 2 0.02 0.026 0.008 1.63 73.7 3 0.03 0.032 0.008 1.71 68.9 4 0.08 0.036 0.01 1.65 66.7 5 0.1 0.038 0.012 1.50 63.8 6 0.02 0.034 0.004 1.46 67.6 7 0.07 0.03 0.004 1.62 72.7 8 0.06 0.035 0.004 1.65 67.0 9 0.06 0.038 0.004 1.69 65.1 10 0.02 0.03 0.005 1.35 70.9 11 0.04 0.028 0.005 1.40 73.8 12 0.02 0.036 0.003 1.52 67.3 13 0.01 0.03 0.004 1.33 72.2 Conventional example One 0.15 0.04 0.017 1.87 61.5 2 0.06 0.04 0.009 1.98 60.8 3 0.01 0.042 0.006 2.08 60.0

As shown in Table 3, it can be seen that the pretreatment of the molten iron according to the present invention is excellent in the pretreatment effect compared to the case of pretreatment by the conventional method.

As described above, the present invention has the effect of achieving a preliminary treatment effect (deregulation effect, dephosphorization effect, and demineralization effect) more economically by using the molten iron preliminary treatment using the ladle slag as steel by-products.

Claims (2)

In a method of pretreatment of molten iron by adding sintered ore at the time of not more than 20% of the total pretreatment time to the molten iron molten reaction vessel, and adding quicklime (CaO) during the preliminary treatment, A ladle slag containing CaO: 35 to 45% by weight, SiO ₂ : 5 to 15% by weight, and Al ₂ O ₃ : 20 to 35% by weight at a time within 20% of the total pretreatment time is placed on the molten iron. The molten iron pretreatment method characterized in that it is added to the reaction vessel so that the basicity (Ca0 / SiO ₂ ) of the produced slag is 1.2 to 1.7. The method of claim 1, wherein the input amount of the ladle slag satisfies the value determined by Equation (1) below. (Equation 1) Ladle slag dose (kg) = {melt dose (ton) x molten iron [Si] (wt%) × 3-CaO dose (kg)} × 4