JP2007332403A - Method for desulfurizing molten iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for desulfurizing molten iron by which when desulfurized slag generated in the desulfurizing treatment of the molten iron is reused as a desulfurizing agent, the potential heat of the desulfurized slag is effectively applied and the desulfurizing treatment can stably be performed by securing the desulfurizing performance. <P>SOLUTION: The above problem is solved by performing as the following: the desulfurized slag 4 generated in the desulfurizing treatment of the molten iron is charged into a desulfurizing treatment vessel 6 under state of hot slag as a part of the desulfurizing agent, and successively, the molten iron 8 is charged into this desulfurizing treatment vessel and thereafter, the molten iron is desulfurized by adding new desulfurizing agent 10 into the molten iron. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hot metal desulfurization treatment method in which desulfurization slag produced by hot metal desulfurization treatment is reused as a hot metal desulfurization agent in a hot metal state.

  The hot metal discharged from the blast furnace usually contains a high concentration of sulfur (S), which adversely affects the quality of the steel. Depending on the required quality of the steel, various types of hot metal and molten steel are used. Desulfurization treatment is performed. However, comparing hot metal and molten steel, the oxygen potential is low, which is advantageous for desulfurization reaction, or because the content of the component that increases the activity of sulfur, that is, the component that promotes desulfurization reaction is high. However, the desulfurization reaction is more efficient, and therefore, the desulfurization treatment is usually performed in the hot metal stage. Various desulfurization agents are used in this hot metal desulfurization method, but since they are inexpensive, in recent years, CaO-based desulfurization agents mainly composed of lime (hereinafter referred to as “CaO”) have been widely used. ing. In this case, the desulfurization reaction proceeds based on the reaction formula shown by “CaO + S → CaS + O”.

  By the way, slag produced in a dry smelting process or refining process such as iron ore reduction smelting, hot metal decarburization refining, or hot metal dephosphorization treatment is usually performed after blast furnace cement, It is reused for concrete materials, fertilizers, roadbed materials, road materials and civil engineering materials. However, desulfurization slag produced by hot metal desulfurization treatment contains high concentration of sulfur and is not suitable for cement materials. Therefore, the present situation is that desulfurization slag is difficult to reuse.

  Then, the method of reusing desulfurization slag as a desulfurization agent of hot metal is proposed for the main purpose of reducing the generation amount of desulfurization slag. For example, in Patent Document 1, desulfurization slag generated in hot metal desulfurization treatment is dropped into another desulfurization treatment vessel in the form of hot metal, and after receiving hot metal in this desulfurization treatment vessel, a new desulfurization agent is added. There has been proposed a method of performing a desulfurization process using only reused desulfurization slag without supplying any slag. However, in the method of Patent Document 1, since only the desulfurization slag is used as the desulfurization agent, the desulfurization ability of the desulfurization slag may be reduced as in the case of repeated reuse of the desulfurization slag, In this case, there is a problem that the desulfurization treatment cannot be performed up to the target concentration range.

In Patent Document 2, desulfurization slag generated by the desulfurization treatment of another hot metal is introduced into another hot metal as a part of the desulfurizing agent in a hot metal state, and then a new CaO-based desulfurizing agent is added to the hot metal. A method of desulfurization treatment has been proposed. In Patent Document 2, since a new desulfurizing agent is added to the desulfurized slag to be reused, the problem in Patent Document 1 is solved. However, the method of Patent Document 2 recovers the desulfurized slag once in a slag recovery container. Alternatively, the desulfurized slag is temporarily discharged to the slag discharge area and temporarily stored, and after receiving the hot metal in the desulfurization treatment container, the desulfurization slag or slag discharge area recovered in the slag recovery container is stored. Temporarily placed desulfurized slag is charged onto the hot metal, so the time from the generation and recovery of desulfurized slag to the charging into the desulfurization treatment vessel becomes longer, while the heat retained in the desulfurized slag is surrounded by the surroundings. There is a problem in that the merit of reusing high-temperature desulfurization slag is reduced due to outflow and waste.
JP-A-63-219514 JP-A-2005-240145

  As described above, when the desulfurization slag generated in the hot metal desulfurization treatment is reused as a desulfurization agent, the conventional method ensures desulfurization ability and stably performs the desulfurization treatment, and the desulfurization slag to be reused. At the same time, we have not achieved effective utilization of the heat stored in the area, and there are still many points that need improvement.

  The present invention has been made to solve such conventional problems, and effectively utilizes the retained heat of the desulfurized slag when the desulfurized slag generated by the desulfurization treatment of the hot metal is reused as a desulfurizing agent. An object of the present invention is to provide a hot metal desulfurization treatment method capable of stably performing the desulfurization treatment while ensuring the desulfurization capability, thereby reducing the desulfurization cost of the hot metal and the generation amount of the desulfurization slag. To do.

  In order to solve the above-mentioned problems, the present inventors have focused on how to use the retained heat of high-temperature desulfurization slag, that is, desulfurization slag in a hot metal state, for another desulfurization treatment. In other words, if the retained heat of the desulfurized slag can be effectively utilized when reused, the temperature drop of the hot metal can be reduced even if a new desulfurizing agent is added, and desulfurization is performed under conditions as high as possible. Processing can be performed. This is because the desulfurization reaction is more advantageous as the temperature is higher, and performing the desulfurization process at a higher temperature also leads to the efficiency of the desulfurization process.

  Therefore, from the viewpoint of how the heat of the high-temperature desulfurization slag can be utilized for the next and subsequent desulfurization treatments, the recovered desulfurization slag is added to the desulfurization treatment vessel for performing the subsequent and subsequent desulfurization treatments by various addition methods. The behavior of the hot metal temperature at that time was investigated. The tested desulfurization treatment methods are six types of desulfurization treatment methods 1 to 6 shown in Table 1.

  Hereinafter, six types of desulfurization treatment methods will be specifically described.

  Desulfurization treatment method 1: Hot metal desulfurization treatment is performed using a CaO-based desulfurization agent, and the high-temperature desulfurization slag generated by this desulfurization treatment is once slag using a scraping-type degreasing machine (also referred to as “slag dragger”). The desulfurized slag discharged and collected in a recovery container is charged into an empty desulfurization treatment container (hot metal ladle) from the slag collection container, and the desulfurization target hot metal discharged from the blast furnace is stored in this desulfurization treatment container. A method of injecting hot metal from the hot metal transfer container and then adding a new CaO-based desulfurization agent to the hot metal and stirring the hot metal using a refractory stirring blade (also referred to as “impeller”) to desulfurize the hot metal.

  Desulfurization treatment method 2: Hot metal desulfurization treatment was performed using a CaO-based desulfurization agent, and high-temperature desulfurization slag generated by this desulfurization treatment was directly charged into another desulfurization treatment vessel using a scraping-type dehumidifier. After that, hot metal is poured into the desulfurization treatment container from the hot metal transfer container containing the hot metal to be desulfurized discharged from the blast furnace, and then a new CaO-based desulfurization agent is added to the hot metal to make a refractory stirring blade. A method of desulfurizing a hot metal with stirring.

  Desulfurization treatment method 3: Hot metal desulfurization treatment is performed using a CaO-based desulfurization agent, and the high-temperature desulfurization slag generated by this desulfurization treatment is once discharged and recovered into a slag recovery container using a scraping-type dehumidifier. In addition, after pouring hot metal into the desulfurization treatment container from the hot metal transfer container containing the desulfurization target hot metal discharged from the blast furnace, the desulfurization slag collected in the slag collection container is charged into this desulfurization treatment container, and then a new A method of adding a CaO-based desulfurizing agent to the hot metal and desulfurizing the hot metal using a refractory stirring blade.

  Desulfurization treatment method 4: Hot metal desulfurization treatment is performed using a CaO-based desulfurization agent, and the high-temperature desulfurization slag generated by this desulfurization treatment is temporarily discharged to a slag waste disposal site using a scraping-type dehumidifier. The hot metal is poured from the desulfurization slag temporarily placed in the desulfurization treatment container after pouring the hot metal into the desulfurization treatment container from the hot metal transfer container containing the desulfurization target molten iron discharged from the blast furnace. The high-temperature desulfurization slag collected using slag is charged, and then a new CaO-based desulfurization agent is added to the hot metal and the hot metal is stirred using a refractory stirring blade to desulfurize the hot metal.

  Desulfurization treatment method 5: Hot metal desulfurization treatment was performed using a CaO-based desulfurization agent, and high-temperature desulfurization slag generated by this desulfurization treatment was directly charged into another desulfurization treatment vessel using a scraping-type degreasing machine. After that, hot metal was poured into the desulfurization treatment container from the hot metal transfer container containing the hot metal to be desulfurized from the blast furnace, and then only desulfurized slag was used as a desulfurizing agent without newly adding a CaO-based desulfurizing agent. A desulfurization treatment method in which the hot metal is stirred using a refractory stirring blade.

  Desulfurization treatment method 6: Hot metal desulfurization treatment was performed using a CaO-based desulfurization agent, and after the desulfurized hot metal was discharged, the hot metal containing the desulfurization target hot metal discharged from the blast furnace was contained in the desulfurization treatment vessel. A method of injecting hot metal from a transfer container, and then adding only a CaO-based desulfurizing agent without adding desulfurization slag and stirring the hot metal using a refractory stirring blade to desulfurize the hot metal. This is a conventional desulfurization method.

  As a result of these six types of desulfurization treatment, as in the desulfurization treatment method 3 and desulfurization treatment method 4, hot desulfurization slag is once discharged to a slag collection container and a waste disposal site, and the desulfurization treatment container is used for hot metal melting. Compared with the case where desulfurization slag is charged into the desulfurization treatment container after receiving the desulfurization treatment, desulfurization slag is charged in advance into the desulfurization treatment vessel used for the next desulfurization treatment as in desulfurization treatment method 1 and desulfurization treatment method 2. In addition, it was found that the hot metal temperature after receiving the hot metal was higher when the hot metal was received thereafter. In particular, as in the desulfurization treatment method 2, when the desulfurization slag was directly charged into the next desulfurization treatment container, it was confirmed that the hot metal temperature was increased.

  Compared to the case where the desulfurization treatment container before receiving is empty, the addition of hot desulfurization slag suppresses the heat dissipation loss of the desulfurization treatment container when empty, and at the same time, This is because the temperature drop of the desulfurized slag itself was reduced by heat.

  Moreover, compared with the case where the desulfurization slag is not reused as in the desulfurization treatment method 6, the case where the desulfurization slag in the hot metal state is reused as in the desulfurization treatment methods 1 to 5 There was little decrease in hot metal temperature. The decrease in the hot metal temperature during the desulfurization treatment was the smallest when only the desulfurization slag was used as the desulfurization agent as in the desulfurization treatment method 5, but in this case, the hot metal sulfur concentration after the treatment was different from that of the other. It was found that the desulfurization treatment up to the target value may not be obtained in some cases.

  From these results, when the desulfurization slag generated in the hot metal desulfurization process is reused in the hot metal state, the desulfurization slag generated in the hot metal desulfurization process is firstly used as in the desulfurization process method 1 and the desulfurization process method 2. The desulfurization treatment vessel was charged, and then the hot metal was charged into the desulfurization treatment vessel. After that, a new desulfurization agent for ensuring the desulfurization capability was added to the hot metal, and desulfurization treatment was performed. It has been found that the target desulfurization ability can be stably obtained.

  That is, when the desulfurization slag generated by the desulfurization treatment of hot metal is reused as a desulfurization agent, the following two points were found to be important.

  (1): In order to stably perform desulfurization treatment according to the target desulfurization amount, desulfurization slag generated by desulfurization treatment of another hot metal is used as a desulfurization agent, and a new desulfurization agent is used in combination with this. To do.

  (2): In order to minimize the heat loss in the desulfurization process of the desulfurization treatment vessel and the desulfurization slag, the desulfurization slag is reused in the hot metal state, and the desulfurized slag in the hot metal state receives the hot metal. Prior to dredging, the desulfurization vessel is charged in advance.

  Here, the desulfurized slag in the hot metal state means desulfurized slag having a temperature higher than room temperature, but from the viewpoint of effectively utilizing the heat of the desulfurized slag, it is desulfurized slag of at least 100 ° C., preferably 500 Desulfurization slag of over ℃ shall be inserted.

  The present invention has been made on the basis of the above knowledge, and the hot metal desulfurization treatment method according to the first invention is based on the desulfurization slag generated in the hot metal desulfurization treatment as a part of the desulfurizing agent and desulfurized. It is characterized in that it is charged in a treatment vessel, and then molten iron is charged in the desulfurization treatment vessel, and then a new desulfurizing agent is added to the molten iron for desulfurization treatment.

  In the hot metal desulfurization method according to the second invention, in the first invention, the desulfurization slag generated in the hot metal desulfurization process is once discharged into a slag collection container, and the desulfurization slag is stored in the slag collection container, The desulfurization slag is charged into the desulfurization treatment container from the slag recovery container.

  The hot metal desulfurization treatment method according to the third invention is the method of the first invention, wherein the desulfurization slag generated in the hot metal desulfurization treatment is directly applied from the vessel to the desulfurization treatment vessel by tilting the container containing the desulfurized hot metal. It is characterized by charging.

  A hot metal desulfurization treatment method according to a fourth invention is characterized in that, in any of the first to third inventions, the temperature of the desulfurization slag is 500 ° C. or more.

  According to the present invention, since the hot metal desulfurization slag is charged in advance before the hot metal is charged into the desulfurization treatment container, the desulfurization slag functions as a heat insulating material, and the amount of heat released from the desulfurization treatment container is reduced. Further, the temperature drop of the desulfurization slag itself is reduced by the heat of the desulfurization treatment container, and the heat loss of the desulfurization treatment container and the desulfurization slag can be greatly reduced as compared with the conventional case. Further, since a new desulfurizing agent is used in combination with the reused desulfurizing slag as the desulfurizing agent, the desulfurization ability is prevented from being lowered and stable desulfurization can be achieved up to the target sulfur concentration. As a result, a reduction in the desulfurization treatment cost and a reduction in the amount of desulfurization slag are achieved, and a beneficial effect is brought about on the industrial and global environment.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic view showing the desulfurization processing method of the first embodiment according to the present invention for each process. First, the desulfurization processing method of the first embodiment shown in FIG. 1 will be described.

  A refractory stirring blade (not shown) attached to the tip of the mechanical stirring device 2 is immersed in a hot metal (not shown) contained in the desulfurization treatment vessel 1, and the stirring blade is swung. The hot metal in the desulfurization vessel and the desulfurizing agent are stirred and mixed, and the hot metal is desulfurized (FIG. 1 (A)). The desulfurization agent in this case can be used as a new desulfurization agent (also referred to as a “new desulfurization agent”) or by using a desulfurization slag generated in a desulfurization process prior to this desulfurization process in combination with a new desulfurization agent. It does not matter either.

  When the desulfurization treatment is completed, the desulfurization treatment container 1 containing the molten iron after the desulfurization treatment is transported to the waste disposal site, and the molten iron after the desulfurization treatment is used by using the scraping-type remover 3 installed in the waste disposal site. The desulfurization slag 4 floating above is scraped out from the desulfurization treatment container 1 to the slag collection container 5 (FIG. 1B). When a predetermined amount of desulfurization slag 4 has accumulated in the slag collection container 5, the slag collection container 5 is moved from directly below the desulfurization treatment container 1 by a hoist or the like. Thereafter, the remaining desulfurization slag 4 staying in the desulfurization treatment container 1 is further scraped out to the waste disposal site, and most of the desulfurization slag 4 is discharged from the desulfurization treatment container 1. In addition, after this discharge, the desulfurization processing container 1 which accommodates the hot metal which has been subjected to the desulfurization process is transported to the next process such as a decarburization refining process or a dephosphorization process.

  Next, a slag collection container 5 containing a predetermined amount of desulfurization slag 4 is lifted by a hoist (not shown), and the desulfurization slag 4 in a hot metal state is evacuated from the slag collection container 5 to an empty desulfurization treatment container containing no hot metal. 6 (FIG. 1C). Thereafter, the hot metal 8 accommodated in the hot metal transfer container 7 is poured into the desulfurization treatment container 6 (FIG. 1D).

  The desulfurization treatment container 6 containing the hot metal 8 is transported to a desulfurization treatment site where the mechanical stirring device 2 is installed, and mechanical stirring is performed inside the desulfurization treatment container 6 with the desulfurization slag 4 placed on the hot metal 8. A refractory stirring blade (not shown) attached to the apparatus 2 is lowered, and the stirring blade is immersed in the hot metal 8. Next, with the stirring blade immersed in the hot metal 8, the stirring blade is turned to stir the hot metal 8. By stirring the hot metal 8, the desulfurized slag 4 is dispersed inside the hot metal 8. In this state, a new desulfurizing agent 10 is added to the hot metal 8 from the desulfurizing agent supply device 9 to perform the desulfurization process (FIG. 1 (E)). A new desulfurizing agent 10 is also caught in the hot metal 8, and the hot metal 8 is desulfurized.

  In this desulfurization treatment, in order to promote the desulfurization reaction, the desulfurization aid is added simultaneously with the addition of the desulfurization agent 10, before or after the addition of the new desulfurization agent 10, or over the entire period of the desulfurization treatment period. Is preferably added over the hot metal 8. Here, the desulfurization aid is for preferentially reacting with oxygen in the slag existing in or on the hot metal to reduce the oxygen potential of the hot metal and slag and to promote the desulfurization reaction by the desulfurization agent. It is. As desulfurization aid, metal Al or aluminum dross powder is mainly used. Besides this, atomized powder obtained by atomizing aluminum melt with gas, cutting powder generated when grinding and cutting aluminum alloy, etc. Other Al sources, Si alloys such as ferrosilicon, and Mg alloys can also be used.

  Even after the addition of the predetermined amount of the desulfurizing agent 10 is completed, if the desulfurization process is continued by turning the stirring blade and stirring is performed for a predetermined time, the number of rotations of the stirring blade is decreased and stopped. When the swirling of the stirring blade stops, the stirring blade is raised from the hot metal 8. The generated desulfurization slag rises and covers the hot metal surface, and the desulfurization process of the hot metal 8 is completed in a stationary state.

  Next, the desulfurization processing method of the second embodiment shown in FIG. 2 will be described.

  In the desulfurization processing method of the first embodiment shown in FIG. 1, the desulfurization slag 4 is temporarily stored in the slag recovery container 5, and the desulfurization slag 4 stored in the slag recovery container 5 is charged into the desulfurization processing container 6. On the other hand, in the desulfurization processing method of the second embodiment shown in FIG. 2, the desulfurization slag 4 is directly charged from the desulfurization processing container 1 to the desulfurization processing container 6, and the first embodiment is described. The desulfurization treatment method of the example and the desulfurization treatment method of the second embodiment are the same except that the steps of charging the desulfurization slag 4 into the desulfurization treatment container 6 are different, and the other steps are the same. Is briefly explained.

  The refractory stirring blades attached to the mechanical stirring device 2 are immersed in the hot metal contained in the desulfurization treatment vessel 1 and swirled, and the hot metal and the desulfurizing agent are stirred and mixed to desulfurize the hot metal (see FIG. 2 (A)).

  When the desulfurization treatment is completed, the desulfurization treatment container 1 containing the molten iron after the desulfurization treatment is transported to the waste disposal site, and the molten iron after the desulfurization treatment is used by using the scraping-type remover 3 installed in the waste disposal site. The desulfurization slag 4 floating above is scraped out from the desulfurization treatment container 1 to an empty desulfurization treatment container 6 that does not contain hot metal (FIG. 2B). When a predetermined amount of the desulfurization slag 4 has accumulated in the desulfurization treatment container 6, the desulfurization treatment container 6 is moved from directly below the desulfurization treatment container 1 by a hoist or the like. Thereafter, the remaining desulfurization slag 4 staying in the desulfurization treatment container 1 is further scraped out to the waste disposal site, and most of the desulfurization slag 4 is discharged from the desulfurization treatment container 1. In addition, after this discharge, the desulfurization processing container 1 which accommodates the hot metal after the desulfurization process is conveyed to the next process.

  Next, the hot metal 8 accommodated in the hot metal transfer container 7 was poured into the desulfurization treatment container 6 (FIG. 2C), and then the desulfurization treatment container 6 containing the hot metal 8 was installed with the mechanical stirring device 2. It is conveyed to a desulfurization treatment plant, and a new desulfurizing agent 10 is added to carry out a desulfurization process on the hot metal 8 (FIG. 2 (D)). This desulfurization treatment is performed by the same method as the desulfurization treatment method of the first embodiment described above, including the use of a desulfurization aid.

  Thus, the desulfurization process is performed on the hot metal 8. After the desulfurization treatment, the generated desulfurization slag is discharged from the desulfurization treatment vessel 6. After this exhaust, the desulfurization treatment container 6 containing the molten iron subjected to the desulfurization treatment is transported to the next step such as a decarburization refining step or a dephosphorization treatment step. Here, the desulfurization slag produced | generated by the desulfurization process shown to FIG. 1 (E) and FIG. 2 (D) can be reused as a desulfurization agent in the desulfurization process after the next time. That is, using the produced desulfurized slag as a part of the desulfurizing agent, the desulfurization treatment can be performed on the hot metal by the steps of FIGS. 1A to 1E or the steps of FIGS. 2A to 2D. it can.

In the hot metal desulfurization treatment according to the present invention, various desulfurization agents such as calcium carbide desulfurization agent, soda desulfurization agent, and metallic Mg can be used as the desulfurization agent. For this reason, it is preferable to use a CaO-based desulfurization agent. Moreover, it is preferable to use a CaO-based desulfurization agent that does not contain a fluorine source, such as fluorite, because environmental measures and disposal of slag become easy. As the CaO-based desulfurization agent not containing a fluorine source, quick lime (CaO), dolomite (MgCO ₃ · CaCO ₃ ), slaked lime (Ca (OH) ₂ ), limestone (CaCO ₃ ) and the like can be used. The particle size of the newly added desulfurizing agent 10 is 1 mm or less or several mm or less.

Further, the hot metal to be subjected to the desulfurization treatment according to the present invention may be any component, and for example, desiliconization treatment or dephosphorization treatment may be performed in advance. The desiliconization treatment is a treatment for mainly removing Si in the hot metal by adding an oxygen source such as oxygen gas or iron ore to the hot metal prior to the dephosphorization treatment in order to efficiently perform the dephosphorization treatment. Phosphorus treatment is mainly in hot metal by adding oxygen source such as oxygen gas or iron ore to hot metal and adding quick lime (CaO) as dephosphorization flux to absorb the generated P ₂ O ₅ Is a process of removing P. Incidentally, typical hot metal chemical components before desulfurization treatment are: C: 3.5 to 5.0 mass%, Si: 0.3 mass% or less, S: 0.02 to 0.05 mass%, P: It is 0.1-0.15 mass%, and the hot metal temperature is 1250-1450 degreeC.

  As the hot metal desulfurization treatment method, a powder desulfurizing agent is blown into hot metal using an inert gas such as Ar gas or nitrogen gas as a carrier gas (referred to as “desulfurizing agent blowing method”), and In general, a method of desulfurization by adding a desulfurizing agent to a hot metal bath surface mechanically stirred by a refractory stirrer (referred to as “mechanical stirring desulfurization method”) is generally performed. The hot metal desulfurization treatment method according to the present invention can be applied to either desulfurization method, but is highly effective when applied to a mechanical stirring desulfurization method.

  As described above, according to the present invention, the hot metal desulfurization slag 4 is charged in advance before the hot metal 8 is charged into the desulfurization treatment vessel 6, so that the desulfurization slag 4 functions as a heat insulating material and performs the desulfurization treatment. The amount of heat released from the vessel 6 is reduced, and the temperature drop of the desulfurization slag 4 itself is reduced by the heat of the desulfurization treatment vessel 6 so that the heat loss of the desulfurization treatment vessel 6 and the desulfurization slag 4 is greatly reduced compared to the conventional case. Can do. Moreover, since the new desulfurization agent 10 is used in combination with the reused desulfurization slag as the desulfurization agent, the desulfurization ability is prevented from being lowered and the desulfurization can be stably performed to the target sulfur concentration.

  In addition, this invention is not limited to the range of the said description, A various change is possible. For example, in the above description, the hot metal 8 is charged into the desulfurization processing container 6 from the hot metal conveying container 7, but the hot metal discharged from the blast furnace may be directly received by the desulfurization processing container 6.

  A test was conducted to reuse hot desulfurization slag generated in the hot metal desulfurization treatment as a desulfurization agent in another desulfurization treatment. The test was carried out by six types of desulfurization treatment methods 1 to 6 shown in Table 1 described above. As a desulfurization agent, a CaO-based desulfurization agent containing about 95% by mass of quick lime and about 5% by mass of fluorite was used in all tests. In all tests, the hot metal sulfur concentration before the desulfurization treatment was adjusted to around 0.030% by mass, and the hot metal temperature immediately before receiving in the desulfurization treatment vessel was adjusted to 1380 ° C. Table 2 shows test results such as operating conditions, hot metal temperature transition and hot metal sulfur concentration transition. In the remarks column of Table 2, tests within the scope of the present invention are displayed as “examples of the present invention”, and others are displayed as “comparative examples”.

  As shown in Table 2, the desulfurization treatment method 3 and the desulfurization treatment method 4, when the hot metal desulfurization slag is received in the desulfurization treatment vessel after receiving the hot metal in the desulfurization treatment vessel, or the desulfurization treatment method When the hot metal desulfurization slag was not reused as in No. 6, the hot metal temperature drop at the time of hot metal receiving from the hot metal conveying container to the desulfurization processing container was 30 ° C. 1. When hot desulfurized slag is charged before hot metal is received in the desulfurization treatment vessel as in desulfurization treatment method 2 and desulfurization treatment method 5, the decrease in hot metal temperature when hot metal is received is It was less than 15 ° C., and it was confirmed that the hot metal temperature drop during receiving was reduced to less than half.

  Moreover, the temperature drop of the hot metal during the desulfurization treatment is higher than that in the case where the desulfurization slag in the hot metal state is not reused as in the desulfurization treatment method 6, and the desulfurization in the hot metal state of the desulfurization treatment methods 1 to 5 is performed. When the slag was reused, it was smaller. In particular, in the desulfurization treatment methods 1 and 2 in which the desulfurization slag was charged before receiving the hot metal, the temperature drop of the hot metal during the desulfurization treatment was small. This is because the heat loss of the desulfurization treatment vessel was suppressed by adding desulfurization slag in the hot metal state to the desulfurization treatment vessel before receiving, and at the same time the temperature decrease of the desulfurization slag was reduced by the heat of the desulfurization treatment vessel by.

  Further, when only desulfurization slag was used as a desulfurizing agent as in the desulfurization treatment method 5, the amount of hot metal temperature dropped during the desulfurization treatment was the smallest, but in this case, the hot metal sulfur concentration after treatment was other than that. It was found that the desulfurization treatment up to the target value may not be obtained in some cases.

  From these results, when the desulfurization slag generated in the hot metal desulfurization process is reused in the hot metal state, the desulfurization slag generated in the hot metal desulfurization process is firstly used as in the desulfurization process method 1 and the desulfurization process method 2. The desulfurization treatment vessel was charged, and then the hot metal was charged into the desulfurization treatment vessel. After that, a new desulfurization agent for ensuring the desulfurization capability was added to the hot metal, and desulfurization treatment was performed. It has been found that the target desulfurization ability can be stably obtained.

It is the schematic which shows the desulfurization processing method of the 1st Example of this invention according to process. It is the schematic which shows the desulfurization processing method of the 2nd Example of this invention according to process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Desulfurization processing container 2 Mechanical stirring apparatus 3 Scraping type degreasing machine 4 Desulfurization slag 5 Slag collection container 6 Desulfurization processing container 7 Hot metal conveyance container 8 Hot metal 9 Desulfurization agent supply apparatus 10 Desulfurization agent

Claims (4)

  The desulfurization slag generated in the hot metal desulfurization treatment is charged as a part of the desulfurizing agent into the desulfurization treatment vessel in a hot metal state, and then the hot metal is charged into the desulfurization treatment vessel. A desulfurization treatment method for hot metal, characterized in that a desulfurization treatment is performed by adding an agent.   The desulfurization slag generated in the hot metal desulfurization treatment is once discharged into a slag collection container, the desulfurization slag is stored in the slag collection container, and then the desulfurization slag is charged from the slag collection container into the desulfurization treatment container. The hot metal desulfurization treatment method according to claim 1.   2. The desulfurization treatment of hot metal according to claim 1, wherein the desulfurization slag generated by the desulfurization treatment of the hot metal is directly charged into the desulfurization treatment vessel from the container by tilting the container containing the desulfurized hot metal. Method.   The hot metal desulfurization method according to any one of claims 1 to 3, wherein the temperature of the desulfurization slag is 500 ° C or higher.

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