Desulfurizing method, desulfurizing agent and flux

Abstract

The desulfurization method according to the present invention is a desulfurization method in which a flux comprising secondary refining slag and hydrofluoric acid sludge; and quicklime are added to molten steel, wherein the flux is added such that at least one of the desulfurization rate and the desulfurization speed from the molten steel satisfies a predetermined desulfurization rate standard or a predetermined desulfurization speed standard, thereby expanding slag recycling by reducing the amount of fluorspar used and / or reducing factors causing environmental pollution by reducing fluorine emissions.

Description

Technology Field

[0001] The present invention relates to a desulfurization method, a desulfurizing agent, and a fluxing agent. More specifically, embodiments apply to a desulfurization method, a desulfurizing agent, and a fluxing agent that reduce the use of fluorite. Background Technology

[0002] Generally, the steelmaking process produces slabs by passing through the sequence of a blast furnace, a molten iron pretreatment facility, a converter, a ladle furnace facility, a degassing facility, and a continuous casting facility. This steelmaking process includes the process of charging molten iron into the converter after the converter operation, refining the converter, and then tapping out the molten steel refined in the converter.

[0003] At this time, molten steel is produced by melting iron ore and contains a large amount of impurities. These impurities include, for example, sulfur (S) and phosphorus (P). Therefore, in order to produce high-quality steel products, the steelmaking process may further include a process to remove impurities from the molten steel.

[0004] At this stage, the desulfurization process includes the addition of quicklime to remove sulfur components. However, quicklime has a high melting point, which results in slow reaction efficiency during the desulfurization process.

[0005] To overcome this, the desulfurization process generally includes an additional step of adding a flux that lowers the melting point of quicklime. The flux includes, for example, fluorite (CaF2). However, in this case, there is a problem in that the resulting steelmaking slag contains fluorine components due to the fluorite, causing environmental pollution. The problem to be solved

[0006] The present invention was created to solve the above-mentioned problems, and aims to provide a desulfurization method using a fluxing agent comprising a fluxing agent that replaces fluorspar or includes secondary refining slag and / or hydrofluoric acid sludge, a desulfurizing agent comprising a fluxing agent, and a desulfurization method using a desulfurizing agent in a desulfurization process for removing sulfur from molten steel.

[0007] Furthermore, the present invention was created to solve the above-mentioned problems, and its purpose is to derive the optimal amount of solvent to be input in a desulfurization process, and to provide a desulfurization agent containing the optimal amount of solvent and a desulfurization method using the desulfurization agent. means of solving the problem

[0008] To achieve the above objective, the desulfurization method according to the present invention is a desulfurization method in which a flux comprising secondary refining slag and hydrofluoric acid sludge; and quicklime are added to molten steel, wherein the flux is added to the molten steel in an amount of weight% such that at least one of the desulfurization rate and the desulfurization speed from the molten steel satisfies a predetermined desulfurization rate standard or a predetermined desulfurization speed standard.

[0009] According to specific examples, the predetermined desulfurization rate standard is, The desulfurization rate calculated by is 40.4 or higher, and is the concentration of sulfur (S) in the molten steel after the fluxing agent is introduced into the molten steel, and the It is characterized by being the concentration of sulfur in the molten steel before the flux is introduced into the molten steel.

[0010] According to specific examples, the flux is characterized by being added to the molten steel in an amount of weight% such that, in y=at+b, t represents time, y represents the concentration of sulfur in the molten steel over time, b represents a constant, and a represents a range of -0.0532 to -0.0484.

[0011] According to specific examples, a predetermined desulfurization rate standard is, The desulfurization rate calculated by has a magnitude of 0.0484 to 0.0532, and the above is the concentration of sulfur after time (t) has elapsed following the introduction of the flux into the molten steel, and the , which is the concentration of sulfur for the case where t is 0, and the It is characterized by exhibiting a desulfurization rate.

[0012] According to specific examples, the desulfurization rate is characterized by being calculated based on the change in sulfur concentration in the molten steel when the above t in the molten steel is 10 minutes or less.

[0013] According to specific examples, b is characterized as the concentration of sulfur in the molten steel before the flux and quicklime are added to the molten steel.

[0014] According to specific examples, the flux is characterized by being added to the molten steel in an amount of weight % such that the distribution ratio to the molten steel satisfies a predetermined distribution ratio standard.

[0015] According to specific examples, the flux is characterized by comprising 25 to 30 weight% of CaF₂ and 25 weight% or more of CaO.

[0016] According to specific examples, the flux is characterized by further comprising at least one of 20 weight% or more of Al₂O₃ and 10 weight% or more of SiO₂.

[0017] To achieve the above objective, the desulfurizing agent according to the present invention comprises a fluxing agent including secondary refining slag and hydrofluoric acid sludge; and quicklime; wherein the fluxing agent is characterized in that, with respect to the secondary refining slag, at least one of the desulfurization rate and the desulfurization speed of desulfurization from molten steel is formed at a ratio satisfying a predetermined desulfurization rate standard or a predetermined desulfurization speed standard.

[0018] According to specific examples, the predetermined desulfurization rate standard is, The desulfurization rate calculated by is 40.4 or higher, and is the concentration of sulfur (S) in the molten steel after the fluxing agent is introduced into the molten steel, and the It is characterized by being the concentration of sulfur in the molten steel before the flux is introduced into the molten steel.

[0019] According to specific examples, the flux is characterized by being formed in a ratio to the secondary refining slag such that, in y=at+b, t represents time, y represents the concentration of sulfur in the molten steel over time, b represents a constant, and a represents a range of -0.0532 to -0.0484.

[0020] According to specific examples, a predetermined desulfurization rate standard is, The desulfurization rate calculated by has a magnitude of 0.0484 to 0.0532, and the above is the concentration of sulfur after time (t) has elapsed following the introduction of the flux into the molten steel, and the , which is the concentration of sulfur for the case where t is 0, and the It is characterized by exhibiting a desulfurization rate.

[0021] According to specific examples, b is characterized as the concentration of sulfur in the molten steel before the flux and quicklime are added to the molten steel.

[0022] According to specific examples, the flux is characterized by being formed such that the distribution ratio to the molten steel with respect to the secondary refining slag satisfies a predetermined distribution ratio standard.

[0023] According to specific examples, the flux is characterized by comprising 25 to 30 weight% of CaF₂ and 25 weight% or more of CaO.

[0024] According to specific examples, the flux is characterized by further comprising at least one of 20 weight% or more of Al₂O₃ and 10 weight% or more of SiO₂.

[0025] According to specific examples, a flux comprising secondary refining slag and hydrofluoric acid sludge is characterized by containing 25 to 30 weight% of CaF₂ and 25 weight% or more of CaO.

[0026] According to specific examples, the flux is characterized by further comprising at least one of 20 weight% or more of Al₂O₃ and 10 weight% or more of SiO₂. Effects of the invention

[0027] Specific examples provide a method to reduce the use of fluorite in the desulfurization process.

[0028] Specific examples provide a method to prevent environmental pollution in the desulfurization process.

[0029] Specific examples provide a method for calculating the optimal amount of solvent to be input into a desulfurization process.

[0030] The effects obtainable from the embodiments are not limited to those mentioned above. Unmentioned effects may be derived or understood by a person skilled in the art based on the various embodiments described in this specification. Brief explanation of the drawing

[0031] FIG. 1 is a diagram schematically illustrating the introduction of a desulfurizing agent into molten steel according to specific examples. Figure 2 is a graph and table showing the experimental results of adding a desulfurizing agent to molten steel according to specific examples. FIG. 3 is a flowchart illustrating a method for determining the composition of a solvent according to specific examples. Figure 4 is a table showing the composition of the solvent determined according to Figure 3. Specific details for implementing the invention

[0032] The present invention will be described below with reference to the attached drawings.

[0033] In this process, the thickness of lines or the size of components depicted in the drawings may be exaggerated for the sake of clarity and convenience of explanation. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intent or convention of the user or operator. Therefore, the definitions of these terms should be based on the content throughout this specification.

[0035] FIG. 1 is a diagram schematically illustrating the introduction of a desulfurizing agent into molten steel according to specific examples.

[0036] In FIG. 1, 10 represents molten steel. The molten steel (10) contains impurities. The impurities include, for example, sulfur (S). The process of removing sulfur (S) from the molten steel (10) is called a desulfurization process, and the method of removing sulfur (S) from the molten steel (10) is called a desulfurization method.

[0037] In order to perform a desulfurization process on molten steel (10), the embodiments provide a desulfurizing agent. In addition, the embodiments provide a desulfurization method using such a desulfurizing agent. For example, the desulfurization method according to the embodiments includes the step of introducing such a desulfurizing agent into the molten steel (10) during the process of tapping the molten steel (10) from a converter. Accordingly, the desulfurizing agent according to the embodiments forms slag from the molten steel (10). Through this, the desulfurizing agent according to the embodiments removes all or part of the sulfur (S) from the molten steel (10). The desulfurizing agent according to the embodiments will be described in more detail below.

[0038] The desulfurizing agent includes quicklime (11) and a flux.

[0039] Quicklime (11) is CaO. Quicklime (11) is added to molten steel (10) and combines with sulfur ions. That is, sulfur (S) combines with Ca+ ions contained in quicklime (11) to produce slag in the form of CaS. Through this, the embodiments can remove all or part of the sulfur (S) from the molten steel (10).

[0040] At this time, the steelmaking process in which molten steel (10) is discharged is carried out at a smelting temperature of, for example, about 1350 to 1600 degrees. Meanwhile, the melting point of quicklime (11) is about 2600 degrees. Accordingly, since the melting point of quicklime (11) is higher than the smelting temperature, the rate of regeneration is slowed down and the reaction efficiency may decrease. To solve this, the desulfurizing agent according to the specific examples includes a fluxing agent.

[0041] Flux is a material that lowers the melting point of quicklime (11). For example, flux includes secondary refining slag (12) and hydrofluoric acid sludge (13).

[0042] The secondary refining slag (12) is slag generated through a secondary refining operation. Thus, the embodiments provide a method to expand the recycling of slag by forming a flux containing the secondary refining slag (12).

[0043] Hydrofluoric acid sludge (13) is sludge containing fluoride ions (F-). Hydrofluoric acid sludge (13) includes, for example, waste sludge generated in semiconductor processes. The embodiments reduce the melting point of quicklime (11) through the fluoride ions (F-) contained in the hydrofluoric acid sludge (13). Additionally, the embodiments improve the dissolving properties by lowering the viscosity of the slag through the fluoride ions (F-). Thus, the embodiments provide a method for expanding the recycling of waste sludge by forming a solvent containing hydrofluoric acid sludge (13).

[0044] The flux contains CaF₂ and / or CaO. For example, the flux contains CaF₂ and / or CaO contained in secondary refining slag (12) and / or hydrofluoric acid sludge (13).

[0045] The fluxing agent includes, for example, CaF₂. CaF₂ includes fluoride ions (F-). The fluoride ions (F-) depolymerize within the molten steel (10). For example, the fluoride ions (F-) depolymerize with the silicate crystal structure of the molten steel (10) or the slag contained in the molten steel (10) (e.g., slag already contained in the molten steel (10) or additionally added slag (e.g., 12)) to lower the melting point and / or viscosity of the molten steel (10) or the slag contained in the molten steel (10). By doing so, the desulfurizing agent containing the fluxing agent according to the embodiments improves the annealing ability of the molten steel (10) or the slag contained in the molten steel (10). Additionally, the fluxing agent includes, for example, CaO. By doing so, the desulfurizing agent containing the fluxing agent according to the embodiments further improves the desulfurization ability.

[0046] Additionally, the flux may further include at least one of Al₂O₃ and / or SiO₂. For example, the flux may further include at least one of Al₂O₃ and / or SiO₂ contained in the secondary refining slag (12) and / or hydrofluoric acid sludge (13). By doing so, the desulfurizing agent containing the flux according to the embodiments lowers the melting point of the desulfurizing agent or the molten steel (10) into which the desulfurizing agent is added and improves the desulfurization efficiency and / or desulfurization efficiency.

[0047] Meanwhile, the flux may include a wider variety of compositions in addition to the compositions described above. For example, the flux may be included in the secondary refining slag (12) and / or hydrofluoric acid sludge (13). It may also include additional components such as , S. However, since such components do not constitute essential components of the solvent, they may be omitted.

[0048] Thus, the desulfurizing agent according to the embodiments provides a method comprising a fluxing agent that replaces fluorite. In addition, the embodiments provide a method that increases desulfurization efficiency while reducing environmental pollution.

[0049] Meanwhile, to ensure high quality and reduce factors causing environmental pollution by lowering fluorine emissions, it is required that an optimal amount of desulfurizing agent be added to the desulfurization process. For example, it is required that an optimal amount of flux be added to the desulfurization process. Below, a method for determining the optimal amount of flux to be added to the desulfurization process is explained.

[0050] Figure 2 is a graph and table showing the experimental results of adding a desulfurizing agent to molten steel according to specific examples.

[0051] As described in FIG. 1, the desulfurizing agent according to the specific examples and the desulfurizing method using such desulfurizing agent provide a method for determining the optimal amount of fluxing agent to be added to the molten steel (10).

[0052] According to the specific examples, the flux is added to the molten steel (10) in an optimal amount. For example, the flux is added to the molten steel (10) in a weight% amount such that at least one of the desulfurization rate and / or desulfurization speed from the molten steel (10) satisfies a predetermined desulfurization rate standard or a predetermined desulfurization speed standard. In FIG. 2, a method for calculating the desulfurization rate and / or desulfurization speed is described as a factor for deriving the optimal amount of flux added to the molten steel (10).

[0053] Figure 2(a) is a graph showing the experimental results of adding a desulfurizing agent (e.g., the desulfurizing agent described in Figure 1) according to specific examples to molten steel (10).

[0054] In FIG. 2(a), the horizontal axis represents time (minutes). At this time, time is the time elapsed after the desulfurizing agent (or flux included in the desulfurizing agent, hereinafter the same) according to the specific examples is introduced into the molten steel (10). In FIG. 2(a), the vertical axis represents the concentration (ppm) of sulfur (S) in the molten steel (10). FIG. 2(a) is an experimental graph showing the change in sulfur (S) concentration over time after the desulfurizing agent according to the specific examples is introduced into the molten steel (10). FIG. 2(b) is a table showing the experimental results of introducing the desulfurizing agent according to the specific examples into the molten steel (10).

[0055] For example, in FIG. 2(a), the concentration of sulfur is shown when the time elapsed after the desulfurizing agent is introduced into the molten steel (10) is 0 minutes, 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 30 minutes.

[0056] First, a method for calculating the desulfurization rate using the desulfurization method according to specific examples is explained. The desulfurization rate is calculated by [Equation 1] below.

[0057]

[0058] At this time, is the concentration of sulfur (S) in the molten steel (10) after time (t) has elapsed since the fluxing agent was introduced into the molten steel (10). At this time, is the concentration of sulfur (S) in the molten steel (10) before the flux is added to the molten steel (10).

[0059] for example, is the concentration of sulfur at a time (t) of approximately 30 minutes after the fluxing agent is introduced into the molten steel (10). At this time, 30 minutes is a time that satisfies the minimum degree of desulfurization required to be removed from the molten steel without waiting for the full time required for 100% desulfurization to occur. 30 minutes is an example and may vary depending, for example, on the amount of molten steel and the amount of desulfurizing agent. Specific examples provide a method for measuring the desulfurization rate after a predetermined time has elapsed after the fluxing agent is introduced in this manner, and deriving the optimal amount of fluxing agent based on the measured desulfurization rate.

[0060] For example, based on [Equation 1], the desulfurization rate is calculated for the experiment described in Fig. 2 (a).

[0061] As illustrated in FIG. 2(a), the comparative example (e.g., using fluorspar as a flux in the conventional operation) has a desulfurization rate of 40.4%. For example, Example 1 (e.g., including 1.5 times the weight% of the fluorspar included in the comparative example as a flux (FSB) replacing fluorspar) has a desulfurization rate of 41.7%. For example, Example 2 (e.g., including 2 times the weight% of the fluorspar included in the comparative example as a flux (FSB) replacing fluorspar) has a desulfurization rate of 37.1%. In this case, Example 1 and Example 2 are examples including a desulfurizing agent according to the specific examples described in FIG. 1. Example 2 represents a case where the amount of flux added to the molten steel (10) is greater than in Example 1. At this time, the desulfurization rates of Comparative Example, Example 1, and Example 2 represent the values ​​when the time (t) is 30 minutes.

[0062] The desulfurization method according to the specific examples allows a flux to be introduced into the molten steel (10) in a weight% amount that satisfies the desulfurization rate standard. At this time, the standard for the desulfurization rate is, for example, the existing operation. For example, the standard for the desulfurization rate is the desulfurization rate derived according to the comparative example. Therefore, the standard for the desulfurization rate can be changed and set according to the standard for the target desulfurization rate.

[0063] For example, according to FIG. 2, the standard desulfurization rate is 40.4%. Accordingly, the desulfurization method according to the specific examples includes the step of adding a fluxing agent to the molten steel (10) in a weight percentage such that the desulfurization rate becomes 40.4% or higher. Through this, the desulfurization method according to the specific examples can guide that adding a smaller amount of fluxing agent to the molten steel (10) is closer to the optimal amount of fluxing agent added than in the case of Example 2.

[0064] However, as described above, the standard for the desulfurization rate may vary depending on the operation, and the standard for the desulfurization rate provided by the specific examples is not limited to 40.4%.

[0065] Next, a method for calculating the desulfurization rate through a desulfurization method according to specific examples is explained. To calculate the desulfurization rate, the specific examples calculate the change in sulfur concentration over a predetermined time in the form y=at+b through linear regression. Here, t represents the time elapsed after the desulfurizing agent is added to the molten steel (10). y represents the sulfur concentration within the molten steel (10) according to time (t) after the fluxing agent is added to the molten steel (10). b is a constant based on the specific examples. b is, for example, the sulfur concentration within the molten steel (10) before the desulfurizing agent is added to the molten steel (10). Here, a is the desulfurization rate. The explanation for a is as follows. In y=at+b, y is , a is It can be calculated in correspondence with. At this time, represents the desulfurization rate. At this time, is the concentration of sulfur (S) in the molten steel (10) before the desulfurizing agent is added to the molten steel (10). is the concentration of sulfur (S) after time (t) has elapsed since the flux was introduced into the molten steel (10).

[0066] At this time, the desulfurization rate can be calculated based on the change in the concentration of sulfur (S) in the molten steel (10) when t is 0 to 10 minutes. However, t is not limited to this and can be any time within 10 minutes, and furthermore, can be applied to a time of 10 minutes or more.

[0067] For example, the results illustrated in FIG. 2(a) can be expressed in the form y=at+b through linear regression over a predetermined time period as described above. Accordingly, for example, as illustrated in FIG. 2(a), the comparative example has a desulfurization rate of 0.0484. For example, Example 1 has a desulfurization rate of 0.0477. For example, Example 2 has a desulfurization rate of 0.0532. In this case, the desulfurization rates of the comparative example, Example 1, and Example 2 represent values ​​when, for example, time (t) is 10 minutes.

[0068] The desulfurization method according to the specific examples allows a flux to be introduced into the molten steel (10) in a weight% amount that satisfies the desulfurization rate standard. At this time, the standard for the desulfurization rate is, for example, a conventional operation. For example, the standard for the desulfurization rate is a desulfurization rate derived according to a comparative example. Therefore, the standard for the desulfurization rate can be changed and set according to the operating environment (for example, the standard for the target desulfurization rate).

[0069] For example, according to FIG. 2, the predetermined desulfurization rate standard is 0.0484. Accordingly, the embodiments add a flux to the molten steel (10) in a weight% amount such that the desulfurization rate becomes 0.0484 or higher. The desulfurization method according to the embodiments can guide that adding a larger amount of flux to the molten steel (10) than in the case of Example 1 is closer to the optimal amount of flux added.

[0070] Preferably, the desulfurization method according to the embodiments can explain a method for finding the optimal amount of solvent to be added by considering both the desulfurization rate and the desulfurization speed. For example, in the case of Example 2, as described above, the desulfurization rate has a value lower than that of the conventional operation. Also, for example, in the case of Example 1, as described above, the desulfurization speed has a value lower than that of the conventional operation. By comprehensively considering these factors, the embodiments indicate that adding solvent so that the magnitude of the desulfurization speed is 0.0484 or higher and 0.0532 or lower is close to the optimal amount.

[0071] Accordingly, for example, the magnitude of the desulfurization rate can be set to 0.0484 to 0.0532, corresponding to the range of a, for example. That is, for example, the predetermined desulfurization rate standard is 0.0484 to 0.0532. The desulfurization method according to the embodiments includes the step of adding a flux to the molten steel (10) in a weight% amount such that the desulfurization rate satisfies the predetermined desulfurization rate standard.

[0072] However, as described above, the predetermined desulfurization rate standard may vary depending on the operation, and the desulfurization rate standard provided by the specific examples is not limited to 0.0484 to 0.0532.

[0073] According to the specific examples, the flux is added to the molten steel (10) in an optimal amount. For example, the flux is added to the molten steel (10) in a weight% amount such that the distribution ratio to the molten steel (10) satisfies a predetermined distribution ratio standard. In FIG. 2, a method for calculating the distribution ratio is further explained as a factor for deriving the optimal amount of flux added to the molten steel (10).

[0074] Next, a method for calculating the distribution ratio through a desulfurization method according to specific examples is explained.

[0075] At this time, the distribution ratio is a factor that affects the desulfurization rate or desulfurization speed. The distribution ratio is calculated through (concentration of S in the slag) / (concentration of S in the molten steel (10)).

[0076] Specific examples allow the flux to be added to the molten steel (10) in a weight percentage that satisfies the distribution ratio of the specified distribution ratio.

[0077] For example, based on the distribution ratio calculation method described above, the desulfurization rate is calculated for the experiment shown in Figure 2 (a).

[0078] As shown in FIG. 2(a), the comparative example has a distribution ratio of 148. For example, Example 1 has a distribution ratio of 124. For example, Example 2 has a distribution ratio of 173. Here, the distribution ratios of the comparative example, Example 1, and Example 2 represent values ​​when time (t) is 30 minutes.

[0079] At this time, the predetermined distribution ratio standard is, for example, the existing operation. For example, the predetermined distribution ratio standard is the distribution ratio derived according to the comparative example. Therefore, the predetermined distribution ratio standard can be changed and set according to the standard of the target desulfurization rate. For example, according to FIG. 2, the predetermined distribution ratio standard is 148. Accordingly, the specific examples allow the fluxing agent to be added to the molten steel (10) in a weight% amount such that the distribution ratio becomes 148 or higher. Through this, the desulfurization method according to the specific examples can guide that increasing the amount of fluxing agent added to the molten steel (10) is closer to the optimal amount of fluxing agent added than in the case of Example 1.

[0080] However, as described above, the distribution ratio standard may vary depending on the operation, and the distribution ratio standard provided by the specific examples is not limited to 148.

[0081] Fig. 2 describes a method for setting factors to be considered in order to calculate the appropriate amount of flux to be added to the molten steel (10). That is, the flux is added to the molten steel (10) in a weight percentage that satisfies at least one of the desulfurization rate, desulfurization speed, and distribution ratio as a desulfurization effect. Specifically, the flux is added to the secondary refining slag (12) in a ratio that satisfies at least one of the above-described factors. At this time, the secondary refining slag (12) is the weight percentage of the secondary refining slag that is initially added to the molten steel (10) in the tapping process.

[0082] Based on exemplary values ​​for the experiment of FIG. 2, a desulfurizing agent containing a flux according to the embodiments may be added to the molten steel (10) in an amount satisfying at least one of 1) a desulfurization rate of 40.4% or more, 2) a desulfurization rate of 0.0484 to 0.0532, and 3) a distribution ratio of 148 or more.

[0083] Below, a method for determining the composition of the solvent, the amount of which has been determined in this manner, is explained.

[0084] Figure 3 explains a method for determining the composition of the solvent introduced in this manner.

[0085] FIG. 3 is a flowchart illustrating a method for determining the composition of a solvent according to specific examples.

[0086] As illustrated in FIG. 3, a method for determining the composition of a solvent (e.g., the solvent described in FIG. 1 and 2) includes a step (s101) of analyzing raw materials and calculating the input amount. At this time, the raw materials are components included in the solvent. The raw materials are, for example, CaF₂, CaO, Al₂O₃, SiO₂, described in FIG. 1. Includes , S, etc.

[0087] As illustrated in FIG. 3, the method for determining the composition of the solvent includes the step (s102) of performing a desulfurization experiment. The desulfurization experiment is represented by a graph such as (a) in FIG. 2, for example.

[0088] As illustrated in FIG. 3, a method for determining the composition of a solvent includes the step (s103) of calculating at least one of a desulfurization rate, a desulfurization rate, and a distribution ratio. The method for calculating at least one of the desulfurization rate, a desulfurization rate, and a distribution ratio is the same or similar as described in FIG. 2.

[0089] As illustrated in FIG. 3, a method for determining the composition of a solvent includes a step (s104) of determining whether at least one of the desulfurization rate, desulfurization speed, and distribution ratio satisfies a predetermined standard. At this time, the predetermined standard is the predetermined desulfurization rate standard, the predetermined desulfurization speed standard, and the predetermined distribution ratio standard described in FIG. 2. If at least one of the desulfurization rate, desulfurization speed, and distribution ratio does not satisfy the predetermined standard, step s101 is performed again.

[0090] As illustrated in FIG. 3, the method for determining the composition of the solvent includes a step (s105) of deriving a final input amount when it is determined that at least one of the desulfurization rate, desulfurization speed, and distribution ratio satisfies a predetermined standard. An example of the derived final input amount is explained through FIG. 4.

[0091] Figure 4 is a table showing the composition of the solvent determined according to Figure 3.

[0092] In FIG. 4, the comparative example (e.g., the comparative example described in FIG. 2) is a case in which fluorite is included as a flux. In FIG. 4, the examples include, for example, Example 1 and Example 2 described in FIG. 2. FIG. 4 shows an example of the final input amount derived according to FIG. 3 based on a predetermined standard set by FIG. 2.

[0093] As illustrated in FIG. 4, the flux according to the embodiments comprises 25 to 30 weight% of CaF₂. In addition, the flux comprises 25 weight% or more of CaO. In addition, the flux may further comprise 20 weight% or more of Al₂O₃. In addition, the flux may further comprise 10 weight% or more of SiO₂. In addition, the flux comprises 0.5 weight% or less It may further include . In addition, the flux may further include 0.5 weight% or less of S. That is, the flux and / or S does not need to be included.

[0094] Through such a composition, specific embodiments provide a solvent satisfying the predetermined criteria described in FIGS. 1 to 3, a desulfurizing agent including the solvent, and a desulfurizing method using the desulfurizing agent.

[0096] Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely illustrative and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the claims below. Explanation of the symbols

[0097] 10: Yonggang 11: Quicklime 12: Secondary refining slag 13: Hydrofluoric acid sludge

Claims

Claim 1 A desulfurization method comprising adding a flux containing secondary refining slag and hydrofluoric acid sludge to molten steel; wherein the flux is added such that at least one of the desulfurization rate and the desulfurization rate obtained from the molten steel satisfies a predetermined desulfurization rate standard or a predetermined desulfurization rate standard, wherein the predetermined desulfurization rate standard is a desulfurization rate calculated by the following Equation 1 that is 40.4 or higher, and the predetermined desulfurization rate standard is a desulfurization rate calculated by the following Equation 2 that has a magnitude of 0.0484 to 0.0532, and wherein the flux is added to the molten steel in an amount of weight% such that, in y=at+b, t represents time, y represents the concentration of sulfur in the molten steel according to the time, b represents a constant, and a represents the range of -0.0532 to -0.0484. t / S0)*100 St: Concentration of sulfur (S) in the molten steel after the flux is added S0: Concentration of sulfur in the molten steel before the flux is added [Equation 2] ln(y t / y0) = -k s *tyt: The concentration of sulfur after time (t) has elapsed following the addition of the flux into the molten steel. y0: The concentration of sulfur for the case where t is 0, and the k s is the desulfurization rate. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A desulfurization method according to claim 1, wherein the desulfurization rate is calculated based on the change in sulfur concentration in the molten steel when t in the molten steel is 10 minutes or less. Claim 6 A desulfurization method according to claim 1, wherein b is the concentration of sulfur in the molten steel before the flux and quicklime are added to the molten steel. Claim 7 In claim 1, the flux is added to the molten steel in an amount of weight % such that the distribution ratio to the molten steel satisfies a predetermined distribution ratio standard, and the predetermined distribution ratio is a distribution ratio calculated by the following Equation 3 that is 148 or higher, a desulfurization method: [Equation 3] Distribution ratio = (Concentration of S in slag) / (Concentration of S in molten steel) Claim 8 A desulfurization method according to claim 1, wherein the solvent comprises 25 to 30 weight% of CaF₂ and 25 weight% or more of CaO. Claim 9 A desulfurization method according to claim 8, wherein the solvent further comprises at least one of 20 weight% or more of Al₂O₃ and 10 weight% or more of SiO₂. Claim 10 A desulfurizing agent added to molten steel, wherein the desulfurizing agent comprises a flux containing secondary refining slag and hydrofluoric acid sludge; and quicklime; A desulfurizing agent comprising, wherein the flux is formed at a ratio such that, with respect to the secondary refining slag, at least one of the desulfurization rate and the desulfurization rate desulfurized from the molten steel satisfies a predetermined desulfurization rate standard or a predetermined desulfurization rate standard, wherein the predetermined desulfurization rate standard is such that the desulfurization rate calculated by the following Equation 1 is 40.4 or higher, and the predetermined desulfurization rate standard is such that the desulfurization rate calculated by the following Equation 2 has a magnitude of 0.0484 to 0.0532, and the flux is formed at a ratio to the secondary refining slag such that, in y=at+b, t represents time, y represents the concentration of sulfur in the molten steel according to the time, b represents a constant, and a represents the range of -0.0532 to -0.0484: [Equation 1] Desulfurization rate = (S t / S0)*100 St: Concentration of sulfur (S) in the molten steel after the flux is added S0: Concentration of sulfur in the molten steel before the flux is added [Equation 2] ln(y t / y0) = -k s *tyt: The concentration of sulfur after time (t) has elapsed following the addition of the flux into the molten steel. y0: The concentration of sulfur for the case where t is 0, and the k s is the desulfurization rate. Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 In claim 10, b is a desulfurizing agent, which is the concentration of sulfur in the molten steel before the flux and quicklime are added to the molten steel. Claim 15 In claim 10, the flux is formed such that the distribution ratio to the molten steel with respect to the secondary refining slag satisfies a predetermined distribution ratio standard, and the predetermined distribution ratio is a distribution ratio calculated by the following Equation 3 that is 148 or higher, a desulfurizing agent: [Equation 3] Distribution ratio = (Concentration of S in slag) / (Concentration of S in molten steel) Claim 16 In claim 10, the solvent is a desulfurizing agent comprising 25 to 30 weight% of CaF₂ and 25 weight% or more of CaO. Claim 17 In claim 10, the solvent is a desulfurizing agent further comprising at least one of 20 weight% or more of Al₂O₃ and 10 weight% or more of SiO₂. Claim 18 delete Claim 19 delete

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