KR100887873B1 - Method for desulfurizing of molten iron using hydrocarbon gas as carrier gas - Google Patents

Abstract

The present invention relates to a desulfurization treatment method in molten iron that can be applied in the production of storage steel, and more particularly, a desulfurization agent blown against molten iron by mixing a proportion of hydrocarbon gas with a conventional nitrogen gas as a feed gas of the desulfurizing agent. It relates to a method for improving the desulfurization reaction efficiency of.

Desulfurizer, desulfurization efficiency, nitrogen gas, hydrocarbon gas, pressurized gas, molten iron, storage steel, TLC, CL

Description

Method for desulfurizing of molten iron using hydrocarbon gas as carrier gas}

1 is an explanatory diagram illustrating a situation where a conventional desulfurization agent and nitrogen gas, which is a pressurized gas, are mixed in a post mix form and blown into molten iron;

2 is an explanatory diagram of a situation in which a desulfurization agent and a nitrogen gas / hydrocarbon gas, which is a pressurized gas, are mixed in a post-mix form and blown into molten iron according to the present invention;

3 is a view illustrating a situation where nitrogen gas is trapped on a surface of CaO, which is a desulfurization agent in the related art;

4 is a view illustrating a situation in which nitrogen + hydrocarbon-based gas is adhered to the surface of CaO, which is a desulfurization agent, and reacts upon blowing according to the present invention;

5 is a graph showing the desulfurization reaction efficiency according to the prior art and the present invention.

The present invention relates to a desulfurization treatment method in molten iron that can be applied in the production of storage steel, and more particularly, a desulfurization agent blown against molten iron by mixing a proportion of hydrocarbon gas with a conventional nitrogen gas as a feed gas of the desulfurizing agent. It relates to a method for improving the desulfurization reaction efficiency of.

At present, the steelmaking process undergoes various refining processes to produce molten steel with high value added and very high purity.

The unrefined molten iron from the furnace is the first process for refining, which is then subjected to desulfurization and, in some cases, desalination.

If sulfur is present in the steel produced as a product, sulfur may cause cracks, deterioration of ductility, and adversely affect steel properties such as red brittleness.

In particular, defects such as rupture of oil transportation pipes, oil well pipes, and cracks in the weld zone are mostly caused by sulfides (MnS) drawn in the rolling direction, and thus are as low as possible except for some free cutting steels to which sulfur is added. Maintains sulfur. Therefore, the priority control of sulfur is important in the steelmaking process, mainly desulfurization in the pretreatment process.

The desulfurization operation of the pretreatment process is carried out in a torpedo ladle car (hereinafter referred to as TLC, Torpedo Ladle Car) or a charging ladle (hereinafter referred to as CL, Charging Ladle), which is a container containing molten iron, and a desulfurization flux. It is blown through a lance to remove sulfur into the slag through reaction with sulfur in the molten iron.

Referring to FIG. 1 showing this process, the desulfurization agent and nitrogen gas, which is a carrier gas, are mixed in a post mix form and blown into the molten iron in TLC or CL through a lance.                         

Here, the post-mix type means that the desulfurization agent and nitrogen gas are mixed at the time of blowing.

At this time, as the desulfurization agent, CaO-based flux is mainly used, and other magnesium (Mg) and soda ash (Na ₂ CO ₃ ) are used, and blowing through the lance of the desulfurization agent is used for desulfurization pumping gas to increase the desulfurization reaction efficiency. Nitrogen (N ₂ ), which is an inert gas, is used without using oxygen or air.

If oxygen is injected, the oxygen potential in molten steel is increased, and the atmospheric oxidizing power is stronger than the stability of sulfur in molten iron, so that oxidation reaction of sulfur occurs and remains in SO ₄ ^2- , SO ₃ state in molten steel. It is difficult to react with Ca ²⁺ ions, while low oxidizing power is not preferable because it exists in the ionic state of S ⁺ and S ² in molten steel and the reaction product is removed in gas or slag form by blowing desulfurization agent.

Therefore, nitrogen gas is generally used as described above. In this case, as illustrated in FIG. 3, nitrogen gas is blown together with the desulfurization agent and trapped on the surface of the desulfurization agent to reduce the CaO reaction surface area of the desulfurization agent. Accordingly, there is a problem in that CaO is inhibited in the rapid reaction when exposed to the molten iron, and the molten iron is lowered during the blowing desulfurization treatment in the molten iron.

The present invention was devised to solve the above problems, and the nitrogen gas which is used as the feed gas of the desulfurizing agent in the conventional molten iron preliminary desulfurization process is adhered to the desulfurizing agent to inhibit the immediate desulfurization reaction when the desulfurizing agent is exposed to molten steel. Since the reaction efficiency is lowered, by using a mixture of hydrocarbon gas with a certain ratio of existing nitrogen gas, oxygen in CaO, a desulfurization agent blown in during blowing through the lance, is reduced to a hydrocarbon gas so that free ion Ca ² is exposed when the desulfurization agent is exposed in molten steel. The purpose of the present invention is to provide a method for improving the desulfurization reaction efficiency by allowing ⁺ to react with sulfur in a short time.

Other objects and advantages of the invention will be described below and will be appreciated by the practice of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the appended claims.

In the desulfurization treatment method for molten iron using the hydrocarbon-based compressed gas of the present invention for achieving the above object, in the desulfurization treatment performed by blowing a CaO-based desulfurization agent through a lance with respect to the molten iron provided from the blast furnace, As a pressurized gas used for blowing, it is characterized by using a mixture of a hydrocarbon-based gas in a predetermined ratio to nitrogen gas.

Preferably, the hydrocarbon-based gas is mixed in a volume amount in the range of 25 to 200% relative to the volume of the nitrogen gas.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 shows a situation in which the desulfurizing agent and the nitrogen gas + hydrocarbon-based gas of the pressurized gas is mixed in the post-mixing form blown into the molten iron in accordance with the present invention.

4 shows a situation in which a hydrocarbon gas is used together as a pressurized gas to replace oxygen in CaO, which is a desulfurization agent, to widen the reaction surface area of the desulfurization agent.

First, the theoretical background on the use of hydrocarbon gas as the pressurized gas will be described.

When the basic desulfurization reaction including CaO, which is a general desulfurization agent, is shown, desulfurization by solid compounds such as quicklime, carbide, and soda ash is a reaction in which a component combined with Ca or Na in the compound is replaced with S in molten iron. The basic formula is:

CaO (s) + [S] = CaS (s) + [O] -------- (one set)

CaC ₂ (s) + [S] = CaS + 2 [C] -------- (2)

Na ₂ CO ₃ + [S] = Na ₂ S + CO ₂ (g) + [O] -------- (3)

In the case of using a CaO-based desulfurization agent during such a desulfurization reaction, according to the present invention, as shown in FIG.

At this time, while the desulfurization agent is transferred to the molten iron by the pressurized gas, the reaction proceeds preferentially by the reaction formula (Formula 4) of CaO, which is the main component of the desulfurizer, and C ₂ H ₂ in the pressurized gas.

5CaO (s) + C ₂ H ₂ (g) → 5Ca (s) + 2CO ₂ (g) + H ₂ O (g) -------- (4)

In this type of reaction, CaO is reduced when passing through the blowing lance, and when the desulfurization agent is exposed to molten iron, it is exposed in the form of Ca ²⁺ to shorten the time for removing oxygen, and secures a wider reaction surface area than the conventional one. In order to improve the reaction efficiency by promoting the desulfurization reaction occurring during the rise per unit time in the slag.

Hereinafter, the embodiment according to the present invention will be described in detail.

<Example>

The experiment was carried out by mixing the hydrocarbon gas in various ratios to the nitrogen gas used as the pressurized gas in the existing pretreatment process, that is, adjusting the mixing ratio.

The desulfurization agent used in the experiment is generally the most widely used high CaO system as shown in Table 1 below.

As a precondition, the pressure in the blown pipe of the pressurized gas was set equal to the atmospheric pressure.

ingredient T. CaO CaF ₂ C ignition loss Content (wt.%) 80.2 3.9 4.3 11.6 standard ≤ 0.15 mm ≤ 0.5mm ≤ 1.0 mm -

Furthermore, the unit used for the desulfurization agent was set and blown by the sulfur content in the molten iron, and the derivation of the experimental results was evaluated as the reaction efficiency (K ') of the desulfurization agent.

The experiment was carried out by mixing nitrogen and hydrocarbon gas on the basis of 1.5Nm ³ / min, the amount of compressed gas used in the existing operation, the ratio is shown in Table 2 below.

division Gas mixing volume (Nm ³ / min) Gas amount (㎏ / min) Nitrogen gas Hydrocarbon gas Nitrogen gas Hydrocarbon gas Conventional example 1.5 - 0.94 - Example 1 1.2 0.3 0.75 0.34 Example 2 1.0 0.5 0.63 0.57 Example 3 0.7 0.8 0.44 0.91 Example 4 0.5 1.0 0.31 1.14

The pressure gas set in this way is the amount currently being applied to prevent the desulfurization agent from forming a blockage when passing through the blowing pipe and to block the desired amount of desulfurization agent.

Mixing of hydrocarbon gas is insufficient to reduce the total amount of oxygen in the blowing desulfurization agent, but only a part of the ratio is mixed to facilitate blowing of the desulfurizing agent.

Desulfurization rate (%) and desulfurization reaction efficiency (K ′) according to each experimental result are shown in Table 3 below.

Here, each experiment was conducted 10 times and averaged, [S] _I represents the initial sulfur content before the treatment, and [S] _f represents the final sulfur content after the treatment, The unit is 10 ^-3 % each.

Desulfurizer raw unit (kg / T) is calculated as "injection (Kg) / molten iron (Ton)", desulfurization rate (%) is calculated as "(sulfur amount before treatment-sulfur content after treatment) * 100" The desulfurization efficiency (K ') is determined by "Ln (sulfur amount before treatment / sulfur amount after treatment) / desulfurizer raw unit".

Here, the desulfurization reaction efficiency (K ') is a data that can compare the desulfurization rate when the input unit is the same, it is possible to evaluate how well the desulfurization reaction was carried out, it can be seen how the hydrocarbon-based gas affected the reaction It is an indicator.

division [S] _I [S] _f Desulfurization Rate (%) Desulfurization Efficiency (K ') Desulfurization Unit (kg / T) Conventional example 27.8 7.8 71.9 0.163 7.8 Example 1 28.5 7.8 72.6 0.168 7.7 Example 2 28.3 6.5 77.0 0.194 7.6 Example 3 27.6 6.3 77.2 0.197 7.5 Example 4 28.9 5.5 81.0 0.213 7.8

Looking at the test results, it can be seen that the desulfurization reaction efficiency is clearly increased when the hydrocarbon gas is not used.

In the case of Example 1, the mixing ratio of hydrocarbon gas is too small, and the reaction efficiency does not show a big difference from the conventional example, but shows a slightly increased result.

However, it can be seen from Example 2 that the desulfurization reaction efficiency greatly increases when the hydrocarbon gas mixture ratio is 0.5 Nm ³ / min or more.

However, in the case of Example 4, clogging of the blown pipe occurred twice out of a total of 10 times during blowing of the desulfurizing agent, which required replacement of the blow lance, resulting in an operation load. This is thought to have occurred because the desulfurization agent was fixed in the blowing pipe by H ₂ O gas or the like due to the reaction of the desulfurization agent with the hydrocarbon gas while the desulfurization agent was blown.

In order to solve this problem, the problem of clogging was solved and the desulfurization reaction efficiency was also increased by increasing the blowing rate of the pressurized gas after desulfurization treatment.

This proved the effect of mixing hydrocarbon gas with a certain amount of existing pressurized gas.

As mentioned above, although this invention was demonstrated by the limited embodiment and drawing, this invention is not limited by this, The person of ordinary skill in the art to which this invention belongs, Of course, various modifications and variations are possible within the scope of the claims to be described below.

According to the present invention, by using a hydrocarbon gas at a predetermined ratio by using only the pressurized gas of the desulfurization agent as nitrogen, the desulfurization reaction efficiency can be improved and stable sulfur control in the molten steel can be achieved even in the production of reservoir steel. It will greatly contribute to stabilization and can reduce the desulfurizer input unit even at the same amount of molten iron, which can bring about significant effects such as reduction in processing time and cost reduction due to the use of expensive desulfurizer.

Claims (2)

In the desulfurization treatment carried out by blowing a CaO-based desulfurization agent through a lance to the molten iron provided from the blast furnace, Desulfurization treatment method of molten iron using a hydrocarbon-based compressed gas, characterized in that for mixing the hydrocarbon-based gas in a volume of 25 ~ 200% by volume relative to the volume of nitrogen gas as the compressed gas used for blowing the desulfurization agent. . delete

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