JP2006265623A - Hot metal pretreatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate undissolved metal which has no danger of water vapor explosion in the dephosphorization process and desiliconization process of hot metal from the slag generated in the dephosphorization process and desiliconization process of hot metal Without using it as an iron source.
In a hot metal pretreatment method in which an oxygen source is supplied to a hot metal to perform dephosphorization or desiliconization, a metal 16 recovered from slag generated by the dephosphorization or desiliconization of the hot metal is obtained. It is added from above the hot metal toward the hot metal before or during the treatment. As a result, there is no danger of steam explosion and it is possible to efficiently use it as an iron source without generating undissolved metal.
[Selection] Figure 1

Description

  The present invention relates to a hot metal pretreatment method in which an oxygen source is supplied to hot metal to perform dephosphorization or desiliconization, and more specifically, a metal recovered from slag generated in dephosphorization and desiliconization of hot metal. The present invention relates to a hot metal pretreatment method that is effectively used as an iron source and performs dephosphorization or desiliconization.

  The hot metal discharged from the blast furnace is often subjected to desulfurization treatment and dephosphorization treatment called hot metal pretreatment before decarburization and refining in the converter. Initially, these pretreatments were carried out for steels that required low sulfidation and low phosphatization due to the quality of the steel materials. However, in recent years, productivity improvement in converters and reduction of Mn ore in converters As a means of reducing the total cost of the steelmaking process in a steelmaking integrated steelworks, desulfurization and dephosphorization treatments have been applied to almost all the hot metal that is produced. It was. In this case, if the silicon content of the hot metal is high, the dephosphorization reaction is inhibited. Therefore, in order to efficiently perform the dephosphorization process, the desiliconization process of the hot metal may be performed prior to the dephosphorization process. This desiliconization process is also one of the hot metal preliminary processes. Since the desulfurization reaction is a reduction reaction, the desulfurization treatment is performed in a reducing atmosphere by adding a CaO-based desulfurization agent or the like to the hot metal, while the dephosphorization reaction and the desiliconization reaction are oxidation reactions. The treatment and the desiliconization treatment are performed by supplying an oxygen source such as oxygen gas or iron oxide to the hot metal.

  After performing this desulfurization process, dephosphorization process, and desiliconization process, the slag which each concentrated the removal object component (sulfur, phosphorus, silicon) generate | occur | produces. In order to prevent the component to be removed in the previous step from being picked up to the molten iron in the subsequent step, the generated slag is removed from the processing container containing the molten iron after the completion of the previous step. The slag removal method includes a method of scraping using a dragger or a method of vacuum suction of the slag, but it is difficult to discharge only the slag by any method. About 30% by mass of metal is mixed.

  Therefore, the discharged slag is crushed after cooling, and the bullion is recovered by magnetically sorting the crushed slag. However, although crushed and magnetically sorted, the slag and the metal are not completely separated, and 30 to 80% by mass of slag is attached to the recovered metal.

  When the recovered metal is used as an iron source, for example, in the decarburization and refining of hot metal in a converter, the phosphorus concentration or sulfur concentration in the molten steel after decarburization and refining increases due to slag adhering to the metal. In order to prevent this, it is necessary to increase the amount of a fouling agent such as quick lime used in decarburization refining, resulting in an increase in production cost. There is no problem if it is used only to such an extent that phosphorus and sulfur in the molten steel after decarburization refining does not rise, but in that case, the generated metal cannot be consumed.

As means for solving this problem, Patent Document 1 has been proposed. In Patent Document 1, bullion generated by hot metal preliminary treatment is classified into three types of desulfurized slag, dephosphorized slag, and desiliconized slab according to the treatment process. Place the gold in the hot metal transport container, receive the hot metal discharged from the blast furnace in the hot metal transport container, melt the bare metal placed with the heat of the hot metal, and desulfurize and dephosphorize this hot metal It is a technology to do. In Patent Document 1, since one kind of bullion is used, only one of phosphorus and sulfur rises. Therefore, there is a merit that it can be adequately handled only by strengthening one of desulfurization treatment or dephosphorization treatment. is there.
JP-A-8-193210

  However, Patent Document 1 has a problem. That is, the slag discharged from the processing container is cooled by the cooling water. Therefore, the collected metal contains about 4 to 20% by mass of moisture, and when receiving it, there is a possibility of causing a steam explosion in the hot metal transport container in which the metal is placed. Therefore, it is necessary to restrict the amount of use to such an extent that steam explosion does not occur.

  In addition, since the placed bullion is mainly melted by the heat of the hot metal, the amount of placement should be adjusted according to the temperature conditions of the hot metal, but the amount of placement should not be constant because it is placed in advance. Therefore, if the storage amount is too much for the hot metal temperature condition, undissolved metal remains at the bottom of the hot metal transport container, and the sulfur concentration or phosphorus concentration in the hot metal is desulfurized. There also arises a problem of picking up after completion of the dephosphorization pretreatment. On the other hand, there may be a case where the amount of storage is too small with respect to the temperature condition of the hot metal, and as a result, the effective utilization of the hot metal heat is not sufficient.

  The present invention has been made in view of the above circumstances, and the object of the present invention is a hot metal pretreatment process using, as an iron source, metal recovered from slag generated in dephosphorization and desiliconization of hot metal pretreatment. In the use in the process, dephosphorization treatment by supplying an oxygen source that can efficiently use the recovered metal as an iron source without the risk of steam explosion and without generating undissolved metal. It is to provide a hot metal pretreatment method for performing desiliconization treatment.

  A hot metal pretreatment method according to a first aspect of the present invention for solving the above-described problem is a hot metal pretreatment method in which an oxygen source is supplied to the hot metal to perform dephosphorization treatment or desiliconization treatment. The bullion recovered from the slag generated by the desiliconization treatment is added to the hot metal from above the hot metal before the start of the treatment or during the treatment period.

  The hot metal preliminary treatment method according to the second invention is characterized in that, in the first invention, the amount of the bare metal added is determined based on a heat balance calculation before and after the treatment.

The hot metal pretreatment method according to a third aspect of the present invention is the hot metal pretreatment method according to the first or second aspect, wherein the hot metal pretreatment method is dephosphorization treatment, and the CaO / SiO ₂ mass ratio of the slag component is 1.0 to 4.0, T. of the slag component. A slag having an Fe concentration of 5% by mass or more is generated on the hot metal and dephosphorized.

  In the hot metal preliminary treatment method according to the fourth invention, in the third invention, the hot metal temperature at the end of the treatment is adjusted to 1250 ° C. to 1400 ° C. by adjusting the supply amount of the gaseous oxygen source from the top blowing lance. It is characterized by controlling to a range.

  According to the present invention, since the bullion recovered from the slag generated in the dephosphorization treatment or desiliconization treatment of hot metal is added on top during the dephosphorization treatment or desiliconization treatment of hot metal, the bullion contains moisture. Even in this case, the water evaporates due to the sensible heat of the hot metal or the sensible heat of the exhaust gas during processing, and can be effectively used as an iron source without worrying about the occurrence of a steam explosion. In addition, the bullion is not added in advance, but the amount of bullion added can be set based on the hot metal temperature and the hot metal component, so that no undissolved bullion is generated, resulting from the undissolved bullion in the subsequent process. Pickup of phosphorus concentration can be prevented. Furthermore, since the slag adhering to the metal is in a so-called pre-melt state once melted, it promotes hatching of a refining additive such as quick lime that is newly added, and in particular promotes a dephosphorization reaction. Although the slag adhering to the bare metal has been used once, it still has a dephosphorization ability and does not hinder the dephosphorization treatment. As described above, the dephosphorization treatment and the desiliconization treatment of the hot metal are promoted more than before, and an industrially beneficial effect is brought about in combination with the effective use of the metal.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing an example of hot metal pretreatment equipment used when carrying out dephosphorization treatment and desiliconization treatment according to the present invention.

  In FIG. 1, a hot metal ladle 2 containing hot metal 13 discharged from a blast furnace (not shown) is mounted on a carriage 3 and carried into a hot metal pretreatment facility 1. The hot metal pretreatment facility 1 is provided with an upper blowing lance 4 and an injection lance 5, and the upper blowing lance 4 and the injection lance 5 can move up and down in the hot metal ladle 2. From the top blowing lance 4, oxygen gas is blown onto the molten iron 13 as a gaseous oxygen source that is a dephosphorizing agent and a desiliconizing agent. The oxygen gas used is industrial pure oxygen, and may contain impurities such as nitrogen gas in a volume percentage of several percent. By using oxygen gas as a dephosphorizing agent and a desiliconizing agent, the temperature of the hot metal 13 rises due to the heat of oxidation. Oxygen-containing gases such as air and oxygen-enriched air can also be used as a gaseous oxygen source, but it is preferable to use oxygen gas because of its high reaction rate.

The injection lance 5 is connected to the storage tank 6 and the storage tank 7, and the powdered solid oxygen source 14 made of iron oxide such as iron ore contained in the storage tank 6 and the powder contained in the storage tank 7. The lime 15 can be blown into the hot metal 13 using a non-oxidizing gas such as nitrogen gas or Ar gas or an inert gas as a carrier gas. The solid oxygen source 14 functions as a dephosphorizing agent or a desiliconizing agent like the oxygen gas. However, although the heat of oxidation is generated by adding the solid oxygen source 14, the temperature of the hot metal 13 is lowered due to the sensible heat and latent heat of the solid oxygen source 14. In the case of dephosphorization, quicklime 15 functions as a dephosphorization flux, melts to form slag 19, reacts with the phosphorous oxide generated by the dephosphorization reaction, and fixes the phosphorous oxide to slag 19. In the case of desiliconization treatment, it reacts with SiO ₂ produced by the desiliconization reaction and adjusts the basicity (CaO / SiO ₂ mass ratio) of the produced slag 19 to form the slag 19. It is for preventing.

  In this case, other fluxes such as fluorite may be mixed with the quicklime 15, and other fluxes may be used instead of the quicklime 15. In addition, the solid oxygen source 14 accommodated in the storage tank 6 and the quicklime 15 accommodated in the storage tank 7 can be blown by independently controlling the addition amount and the addition time, and injection. The hot metal 13 can be stirred by blowing only non-oxidizing gas or inert gas such as nitrogen gas and Ar gas from the lance 5.

  The hot metal preliminary treatment facility 1 is further provided with a raw material supply facility comprising a hopper 8, a hopper 9 and a hopper 10, a raw material transport device 11, and a chute 12. The recovered bullion 16 stored in the hopper 9, the granular or massive solid oxygen source 17 accommodated in the hopper 9, and the granular or massive quick lime 18 accommodated in the hopper 10 are added to the hot metal ladle 2 on top. Can be done. The granular or massive solid oxygen source 17 functions as a dephosphorizing agent and a desiliconizing agent in the same manner as the powdered solid oxygen source 14, and the granular or massive quick lime 18 is dephosphorized in the same manner as the powdered quick lime 15. In the treatment, it functions as a dephosphorization flux for fixing the phosphorus oxide, and in the desiliconization treatment, it functions as a basicity adjustment of the slag 19. As the solid oxygen sources 14 and 17, iron ore, sintered ore, mill scale, dust collection dust, or the like can be used.

  The recovered metal 16 is a slag generated by dephosphorization or desiliconization of hot metal, cooled with cooling water, etc., crushed and classified, and then magnetically sorted. Is included. The size of the recovered metal 16 is not particularly limited, but is required to be a size that can be input by a raw material supply facility including the hopper 8, the raw material transfer device 11, and the chute 12. As long as it is a size that can be charged in this raw material supply facility, it does not matter.

  In this case, the recovered metal 16 recovered from the slag generated by the dephosphorization process (hereinafter referred to as “dephosphorized metal”) and the recovered metal 16 recovered from the slag generated by the desiliconization process (hereinafter “ The term “desiliconized bullion” will be described because the composition of the slag adhering is slightly different. It should be noted that the components of the bullion itself are only slightly lower in the phosphorus and silicon contents of phosphorus and the other components are not much different.

Generally, the slag generated by the dephosphorization treatment has a high slag basicity (CaO / SiO ₂ mass ratio) of about 2-3. This is because the higher the basicity of the slag, the higher the absorption capacity of the phosphor oxide produced by the dephosphorization reaction, and a larger amount of the phosphor oxide can be fixed in the slag. Moreover, 1-2 mass% phosphorus is contained in slag. However, the slag has a dephosphorization ability, and the phosphorus in the slag does not return to the molten iron 13 under an oxidizing atmosphere and the basicity of the slag is about 1 or more.

  Therefore, when dephosphorized metal is used in the dephosphorization process, hatching of quicklime 15 and quicklime 18 is promoted by the slag adhering to the dephosphorized metal, and the dephosphorization reaction may be promoted. The phosphorus in the hot metal 13 is not picked up by the slag adhering to the dephosphorized metal. On the other hand, when the dephosphorized metal is used in the desiliconization process, the CaO content of the slag adhering to the dephosphorized metal functions as a slag basicity adjustment. Even in the desiliconization treatment, since it is in an oxidizing atmosphere, if the basicity of the slag is adjusted to about 1, phosphorus does not return to the hot metal 13 from the slag adhering to the dephosphorized metal. Even if the basicity of the slag is low and phosphorus returns from the slag adhering to the dephosphorized metal to the molten iron 13, the dephosphorization process is refrained in the subsequent process, and the picked-up phosphorus is removed.

  The slag generated by the desiliconization treatment has a basicity of about 1.0 and contains about 1% by mass of phosphorus. Therefore, when the desiliconized bullion is used in the dephosphorization process, the slag adhering to the desilica bullion is also in a premelt state, so that the hatching of the quicklime 15 and the quicklime 18 is promoted and the dephosphorization reaction Is promoted. Although the basicity of the slag produced by the slag adhering to the desiliconized bullion is lowered, it is not particularly addressed. On the other hand, when desiliconized bullion is used in the desiliconization process, there is a demerit that the amount of generated slag increases due to the slag adhering to the desiliconized bullion, but it does not affect the desiliconization reaction, The benefits of recovered iron are much greater.

  Since the recovered metal 16 functions as a coolant in the dephosphorization process and the desiliconization process, it is necessary to consider the mixing ratio with the fixed oxygen sources 14 and 17 that also function as a coolant. In order to fully exhibit the effects of the present invention, it is preferable to suppress the amount of solid oxygen sources 14 and 17 used and increase the amount of recovered metal 16 used. Further, the recovered metal 16 does not need to be separately collected by the dephosphorized metal and the desiliconized metal, but may be used in a processing step generated by separate recovery.

  First, a method for performing hot metal desiliconization processing according to the present invention using the hot metal pretreatment facility 1 having such a configuration will be described.

While the injection lance 5 is immersed in the hot metal 13 and nitrogen gas or Ar gas is blown from the injection lance 5 as a stirring gas, oxygen gas is continuously supplied from the upper blowing lance 4 toward the hot metal 13 accommodated in the hot metal pan 2. The hot metal 13 is desiliconized. The silicon in the hot metal is oxidized by the sprayed oxygen to become SiO ₂ and moves to the slag 19 and the desiliconization reaction proceeds. At that time, quick lime 15 or 18 may be added to adjust the basicity of the slag 19 to be generated. In this case, granular or massive quick lime 18 may be placed in the hot metal hot pot 2 through the chute 12, but from the viewpoint of strengthening the stirring of the hot metal 13, the powdered quick lime is supplied via the injection lance 5. 15 is preferably added by blowing into the hot metal 13. Alternatively, a powdered solid oxygen source 14 may be blown from the injection lance 5 into the molten iron 13, or a granular or massive solid oxygen source 17 may be placed on the molten iron 13 from the chute 12.

  In this desiliconization process, the recovered metal 16 accommodated in the hopper 8 is continuously or intermittently charged into the hot metal ladle 2 through the chute 12. The input amount of the recovered metal 16 is adjusted to a range in which the temperature of the hot metal 13 at the end of the desiliconization process is an arbitrary temperature of 1400 ° C to 1450 ° C.

  Specifically, as shown in FIG. 2, heat input calculation and heat output calculation are performed, and further, a total oxygen source unit including a gaseous oxygen source and a solid oxygen source, a solid oxygen source unit, a quick lime unit In consideration of the unit, the difference heat between the heat input amount and the heat output amount may correspond to the heat source for melting the recovered metal 16. Of course, it may be less than the amount corresponding to the heat of the difference between the heat input amount and the heat output amount. As described above, since the amount of heat output decreases as the solid oxygen source unit decreases, in order to increase the input amount of the recovered metal 16, it is preferable to decrease the solid oxygen source unit. In the calculation method shown in FIG. 2, the amount of heat input increases as the total oxygen source unit increases, and the amount of heat output increases as the quick lime unit increases.

  When the temperature of the hot metal 13 at the end of the desiliconization process is less than 1400 ° C., the sensible heat of the hot metal 13 is reduced, and heat may be insufficient in subsequent converter decarburization refining, which may prevent efficient refining. On the other hand, if it exceeds 1450 ° C., the refractory material of the hot metal ladle 2 and the refractory material of the injection lance 5 become seriously damaged, resulting in an increase in cost.

  The total amount of the recovered metal 16 to be charged may be charged into the hot metal ladle 2 before starting the supply of oxygen gas from the upper blowing lance 4, and before starting the supply of oxygen gas from the upper blowing lance 4. Then, it is possible to divide and collect the recovered metal 16 later. However, when charging during the desiliconization process, it is preferable to complete the predetermined amount before 80% of the desiliconization time has elapsed in order to prevent the recovered metal 16 from being undissolved.

  After the desiliconization process, the hot metal ladle 2 containing the hot metal 13 is conveyed to the waste ironing station, and the slag 19 is discharged from the hot metal ladle 2 using a dragger or the like. The discharged slag 19 is cooled, and after cooling, it is crushed and classified, and further magnetically sorted to recover the desiliconized metal. The recovered desiliconized bullion is used as the recovered bullion 16.

  In this way, by performing the desiliconization process on the molten iron 13, even if the recovered metal 16 contains moisture, the water evaporates due to the sensible heat of the molten iron 13 or the sensible heat of the exhaust gas during the treatment, and the steam explosion The recovery bullion 16 can be effectively used as an iron source without worrying about the occurrence of. Moreover, since the addition amount of the collection | recovery metal 16 can be set based on the hot metal temperature and hot metal component before a process, the collection | recovery metal 16 which remains undissolved does not generate | occur | produce, but it originates in the undissolved metal in a post process. Problems such as phosphorus concentration pick-up can be prevented. Furthermore, since the slag adhering to the recovered metal 16 is in a so-called pre-melt state once melted, the hatching of newly added quicklime 15 and 18 is promoted and the slag 19 is prevented from forming.

  Next, a method for carrying out hot metal dephosphorization processing according to the present invention using the hot metal pretreatment facility 1 having the above-described configuration will be described. In order to efficiently perform the dephosphorization reaction, it is preferable to reduce the silicon content of the hot metal 13 to about 0.2% by mass or less in advance by desiliconization before dephosphorization.

  The injection lance 5 is immersed in the hot metal 13, and nitrogen gas, Ar gas, or the like is blown from the injection lance 5 as stirring gas, and powdered quicklime 15 is blown into the hot metal 13 through the injection lance 5 as dephosphorization flux. Alternatively, granular or massive quicklime 18 is placed on the hot metal 13 through the chute 12, and oxygen gas is continuously blown from the upper blowing lance 4 toward the hot metal 13 accommodated in the hot metal pan 2, The hot metal 13 is dephosphorized. At that time, a powdered solid oxygen source 14 may be blown from the injection lance 5 into the molten iron 13, or a granular or massive solid oxygen source 17 may be placed on the molten iron 13 from the chute 12.

By refining in this way, the phosphorus contained in the hot metal 13 is oxidized by the supplied oxygen gas or oxygen of the solid oxygen sources 14 and 17 to become P ₂ O ₅ , and the quick lime 15 and 18 are melted and generated. The slag 19 is transferred to the dephosphorization reaction.

  In this dephosphorization process, the recovered metal 16 accommodated in the hopper 8 is continuously or intermittently charged into the hot metal ladle 2 via the chute 12. The input amount of the recovered metal 16 is adjusted to a range in which the temperature of the hot metal 13 at the end of the dephosphorization process is 1250 ° C to 1400 ° C, preferably 1250 ° C to 1350 ° C.

  Specifically, as shown in FIG. 3, heat input calculation and heat output calculation are performed, and further, a total oxygen source unit including a gaseous oxygen source and a solid oxygen source, a solid oxygen source unit, a quick lime unit In consideration of the unit, the difference heat between the heat input amount and the heat output amount may correspond to the heat source for melting the recovered metal 16. Of course, it may be less than the amount corresponding to the heat of the difference between the heat input amount and the heat output amount. As described above, since the amount of heat output decreases as the solid oxygen source unit decreases, in order to increase the input amount of the recovered metal 16, it is preferable to decrease the solid oxygen source unit. In the calculation method shown in FIG. 3, the amount of heat input increases as the total oxygen source unit increases, and the amount of heat output increases as the quick lime unit increases. If the temperature of the hot metal 13 at the end of the dephosphorization process is less than 1250 ° C., heat will be insufficient in the subsequent process, preventing normal refining. On the other hand, if the temperature of the hot metal 13 at the end of the dephosphorization process exceeds 1400 ° C. Since the phosphorous reaction does not proceed and dephosphorization cannot be achieved to a predetermined concentration, it is not preferable.

  The total amount of the recovered metal 16 to be charged may be charged into the hot metal ladle 2 before starting the supply of oxygen gas from the upper blowing lance 4, and before starting the supply of oxygen gas from the upper blowing lance 4. Then, it is possible to divide and collect the recovered metal 16 later. However, when charging during the dephosphorization process, it is preferable to complete a predetermined amount of input before 80% of the dephosphorization time has elapsed in order to prevent the recovered metal 16 from being undissolved.

The composition of the slag 19 to be produced has a CaO / SiO ₂ mass ratio of the slag component in the range of 1.0 to 4.0, preferably in the range of 1.5 to 3.0. It is preferable to adjust the usage amounts of quicklime 15 and 18 and the solid oxygen sources 14 and 17 so that the Fe concentration is 5% by mass or more, desirably 10% by mass or more.

When the CaO / SiO ₂ mass ratio of the slag component is less than 1.0, the phosphorus oxide absorption capacity of the slag 19 is low and the dephosphorization reaction is not promoted. If the CaO / SiO ₂ mass ratio of the slag component exceeds 4.0, the absorption capacity of the phosphorous oxide of the slag 19 will be reasonably high, but making it higher than necessary will increase the cost of quick lime. This is not preferable. Since the dephosphorization reaction is an oxidation reaction, it is desirable to increase the oxygen potential of the slag 19. If the Fe concentration is less than 5% by mass, the oxygen potential becomes too low and the dephosphorization reaction is not promoted. T. Fe (total Fe) is the total iron content of all iron oxides (FeO, Fe ₂ O _3, etc.) contained in the slag 19.

  After the dephosphorization treatment, the hot metal ladle 2 containing the hot metal 13 is transported to the waste ironing station, and the slag 19 is discharged from the hot metal ladle 2 using a dragger or the like. The discharged slag 19 is cooled, crushed and classified after cooling, and further magnetically sorted to recover the dephosphorized metal. The recovered dephosphorized metal is used as the recovered metal 16.

  In this way, by dephosphorizing the hot metal 13, even if the recovered metal 16 contains water, the water evaporates due to the sensible heat of the hot metal 13 or the sensible heat of the exhaust gas during processing, and the steam explosion The recovery bullion 16 can be effectively used as an iron source without worrying about the occurrence of. Moreover, since the addition amount of the collection | recovery metal 16 can be set based on the hot metal temperature and hot metal component before a process, the collection | recovery metal 16 which remains undissolved does not generate | occur | produce, but it originates in the undissolved metal in a post process. Problems such as phosphorus concentration pick-up can be prevented. Furthermore, since the slag adhering to the recovered metal 16 is in a so-called pre-melt state once melted, the hatching of newly added quicklime 15 and 18 is promoted and the dephosphorization reaction is promoted.

  In addition, although the said description was performed in the example using the hot metal ladle 2 as a processing container, in implementing this invention, a processing container is not necessarily restricted to the hot metal ladle 2, Even if it is a torpedo car and a charging pan, Even if it is a converter type refining furnace, the present invention can be carried out along the above.

  The hot metal discharged from the blast furnace was received by a hot metal ladle having a capacity of 200 tons and transferred to the hot metal pretreatment facility shown in FIG. At that time, when recovered bullion mixed with dephosphorized bullion and desilica bullion having the composition shown in Table 1 in a mixing ratio of about 1: 1 is previously placed in a hot metal ladle before receiving. (Comparative example) and the case where it was added on top during the dephosphorization treatment (invention example) were carried out at two levels. In addition, for the sake of comparison, the case where no recovered metal was used (conventional example) was also carried out. Table 2 shows the test results.

  As shown in Table 2, in the test (comparative example) in which the collected bullion was placed, undissolved bullion was observed when the collected bullion was used at 15 kg / t. On the other hand, in the test (invention example) added during the treatment, even when the recovered ingot was used at 15 kg / t, undissolved ingot was not recognized, and the molten iron phosphorus concentration after the treatment was ingot. It was equivalent to the conventional example that did not. However, in the test No. 6 in which the hot metal temperature after dephosphorization was 1650 ° C., the hot metal temperature after the treatment was too high and the dephosphorization reaction was not promoted, so the phosphorus concentration in the hot metal after the treatment became high. It was. Therefore, it has been confirmed that it is not preferable to excessively raise the hot metal temperature after the treatment.

It is a schematic sectional drawing which shows an example of the hot metal pretreatment equipment used when implementing this invention. It is a figure which shows the calculation method which determines the input amount of the collection | recovery ingots in a desiliconization process. It is a figure which shows the calculation method which determines the input amount of the collection | recovery bullion in a dephosphorization process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hot metal preliminary processing equipment 2 Hot metal ladle 3 Carriage 4 Top blowing lance 5 Injection lance 6 Storage tank 7 Storage tank 8 Hopper 9 Hopper 10 Hopper 11 Raw material conveyance device 12 Chute 13 Hot metal 14 Solid oxygen source 15 Quick lime 16 Recovery metal 17 Solid oxygen Source 18 Quicklime 19 Slag

Claims (4)

  In the hot metal preliminary treatment method in which an oxygen source is supplied to the hot metal to perform dephosphorization treatment or desiliconization treatment, the metal recovered from the slag generated by the dephosphorization treatment or desiliconization treatment of the hot metal before the start of treatment or the treatment period A hot metal preliminary treatment method, wherein the hot metal is added from above to the hot metal.   The hot metal pretreatment method according to claim 1, wherein the amount of the metal added is determined based on a heat balance calculation before and after the treatment. The hot metal pretreatment method is dephosphorization treatment, wherein the CaO / SiO ₂ mass ratio of the slag component is 1.0 to 4.0, and the slag component T.I. The hot metal pretreatment method according to claim 1 or 2, wherein a slag having an Fe concentration of 5 mass% or more is generated on the hot metal and dephosphorized.   The hot metal temperature at the end of the treatment is controlled in the range of 1250 ° C to 1400 ° C by adjusting the supply amount of the gaseous oxygen source from the top blowing lance. Processing method.

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