JP6828678B2 - Converter refining method - Google Patents

Description

The present invention relates to a converter refining method effective for enhancing the slag discharge capacity during the intermediate slag discharge treatment after the desiliconization treatment by promoting the melting and slag formation of the medium-melting material added to the converter.

In recent years, in the field of steelmaking refining, so-called hot metal pretreatment, which removes silicon and phosphorus in hot metal from a blast furnace prior to decarburization in a converter, has become widespread, and it has become popular with mediators such as lime. It is known to contribute to the reduction of the amount of steelmaking slag generated. However, when this hot metal pretreatment technology is performed in a hot metal transfer container such as a blast furnace pot or a topedo car, heat loss is associated with the transfer of hot metal, so the proportion of cold iron sources such as iron scrap must be suppressed. This is an obstacle to reducing greenhouse gas emissions such as CO ₂ .

Conventionally, a technique has been developed that can advantageously solve the above-mentioned problems, that is, both the merit of so-called hot metal pretreatment and the increase in the selection range of the main raw material. For example, as disclosed in Patent Document 1, there is a method of performing both hot metal pretreatment and decarburization treatment using one converter. This method includes a process of charging scrap iron and hot metal into a converter, a dephosphorization process by adding a filler material (flux) and blowing oxygen, a process of tilting and discharging dephosphorized slag, and decarburizing by adding flux and blowing oxygen. , Dephosphorization, decarburization, steel removal with dephosphorization slag remaining, decarburization, addition of carbonaceous material to dephosphorization slag to reduce iron oxide in slag. It is said that the above-mentioned merits of the hot metal pretreatment can be enjoyed without impairing the productivity.

Further, Patent Document 2 discloses a method of performing desiliconization treatment, dephosphorization treatment and decarburization treatment using two converters. In this method, first, in the first converter, a powder containing refining oxygen and a lime-based medial material is sprayed from a top-blown lance to perform desiliconization treatment, and then a part of the desiliconization treatment slag is intermediately discharged. Then, the hot metal after the desiliconization treatment is sprayed with a powder containing refining oxygen and a lime-based medial material to perform the dephosphorization treatment, and then in the second converter, the hot metal after the dephosphorization treatment is decarburized. How to do it. In this method, in one or both of the desiliconization and dephosphorization treatments, a burner-functioning lance capable of spraying oxygen for refining, powder containing a lime-based medialant, fuel gas and flammable gas is provided. By using it, it is possible to desiliconize and dephosphorize the hot metal with a small amount of medial material.

Japanese Unexamined Patent Publication No. 5-140627 International Publication No. 2014/112432

Kenichiro Naito, 3 others, "Fundamental study of the effects of various factors on the fluid behavior in intermediate slag in the MURC (Multi-Refining Converter) method", Iron and Steel, Nippon Steel & Sumitomo Metal Corporation, 2014 , Vol. 100, No. 4, p. 522-529

Among the above-mentioned prior arts, the method described in Patent Document 1 has a slag basicity of 1.0 in the step of dephosphorizing by adding a medializing material (flux) and blowing oxygen in addition to the above-mentioned contents. By setting the temperature to ~ 2.0 and the temperature to 1350 ° C. or lower, the decrease in dephosphorization ability due to the decrease in basicity is suppressed. However, in the case of this technique, since the melting point of the slag rises sharply in the region where the basicity exceeds 1.0, in order to promote the dissolution of the flux, the rise in the FeO concentration in the slag is suppressed and the temperature is 1350 ° C. or higher. There is a problem that it is necessary to process at the temperature of.

Further, Patent Document 2 has an advantage that even a high melting point flux can be easily dissolved because a high-temperature flame exceeding 2000 ° C. can be used by using a top-blown lance with a burner function. However, in this method, transfer of hot metal occurs due to the use of two converters. Therefore, the heat loss increases and the blending range of iron scrap is restricted. Therefore, if the blending range of iron scrap is exceeded, a new heat source is required, which may cause a problem that the heat source cost increases.

Further, the non-patent document 1 describes an example in which a water model and a numerical analysis simulation for the intermediate discharge process of the converter are performed, but here, the viscosity of the slag is large and the density difference between the slag and the metal is small. It is pointed out that the metal easily flows out and the slag removal property decreases. Therefore, it is necessary to reduce the slag viscosity in order to increase the amount of desiliconized or dephosphorized slag discharged in the intermediate slag removal process of the converter and to enjoy the benefits of reducing the amount of lime and other mediators and steelmaking slag generated. become.

The present invention has been developed in view of the above-mentioned problems of the prior art, and an object of the present invention is to use a top-blown slag to produce powders containing industrial oxygen gas and CaO in the same converter. In the converter refining for producing molten steel from hot metal by spraying the body (medium-melting material) onto the hot metal in the converter to desiliconize and dephosphorize, and further decarburize, the medium-melting material in the converter. By promoting the slag formation and melting, the amount of slag discharged during the intermediate slag treatment after the desiliconization treatment is increased, the iron yield is improved, and the basic unit of the medial material such as CaO powder and granules is reduced. It is to propose a refining method that can be done.

The present invention is a method for solving the above-mentioned problems and realizing the above-mentioned object, and the gist thereof is to follow the desiliconization treatment of hot metal and the subsequent intermediate slag treatment by the same converter . In the converter refining method for producing molten steel by performing dephosphorization and decarburization treatment using the same converter , first, scrap and hot metal are charged into the converter, and then industrial oxygen is supplied from the top blown lance. In the desiliconization treatment performed by spraying a medium-soluble material composed of powders and granules containing gas and CaO onto a hot metal bath surface, an industrial oxygen gas and a medium-soluble material composed of powders and granules containing CaO are top-blown having a burner function. and the heat medium by heating the medium welding material with a lance, by spraying the bath surface of the molten iron or molten steel, which intermediate discharge temperature of the desiliconization treatment slag at desiliconization process end from the 1600 ° C. or higher It is a converter refining method characterized by slag treatment.

Further, more specifically, the present invention manufactures molten steel by performing dephosphorization treatment and decarburization treatment using the same converter, following the desiliconization treatment of hot metal and the subsequent intermediate slag treatment in the same converter. First, scrap and hot metal are charged into the converter, and a medium-melting material composed of powders and granules containing industrial oxygen gas and CaO is sprayed from the top-blown lance onto the hot metal bath surface to desiliconize the hot metal. Next, a part of the slag after the desiliconization treatment is discharged to the outside of the furnace, while the inside of the furnace is composed of the desiliconized hot metal and the residual amount of the slag after the desiliconization treatment. Then, the desiliconized hot metal is dephosphorized and decarburized by spraying a medium-melting material consisting of powders and granules containing CaO together with oxygen gas for refining from the top-blown slag, and then the furnace. While dephosphorization and decarburization treatment of molten steel remaining inside is discharged to a molten steel pot, part or all of the slag remaining in the furnace after dephosphorization and decarburization treatment is discharged to the outside of the furnace to manufacture molten steel. In the converter refining method
In each of the desiliconization, dephosphorization, and decarburization treatments, a medial solution composed of powders and granules containing industrial oxygen gas and CaO is composed of powders and granules containing the CaO using a top blowing slag having a burner function. By heating the medial material to form a heat medium and spraying it onto the hot metal or molten steel bath surface, the desiliconization, dephosphorization and decarburization treatment slags are heated , and the desiliconization treatment is performed at the end of this treatment. A converter refining method is characterized in that the temperature of the desiliconized slag is set to 1600 ° C. or higher and then subjected to an intermediate waste treatment .

According to the present invention configured as described above, in refining in which desiliconization, dephosphorization and decarburization are performed using one converter, a method with high heating efficiency is adopted, that is, powder or granular material containing CaO. By supplying the medium-melting material composed of the above to the hot metal to be treated in the state of a heat medium by a burner of a top-blown lance, heat loss can be reduced and energy consumption can be reduced, and after desiliconization treatment, it is possible to reduce energy consumption. The efficiency of the intermediate waste treatment can be improved. As a result, the amount of slag remaining in the furnace can be reduced.

It is the schematic of the converter equipment which is equipped with the top blowing lance which has a burner function at the time of each process of desiliconization, dephosphorization and decarburization. When CaO-based powder or granular material is sprayed on the hot metal bath surface together with oxygen gas for refining using a top-blown lance equipped with a burner function, the presence or absence of fuel gas (a, b) and the presence or absence of CaO powder (b) , C), and it is a figure which evaluated the slag heating characteristic during the desiliconization treatment. When CaO powder is sprayed on the hot metal bath surface together with oxygen gas for refining using a top-blown lance equipped with a burner function, the presence or absence of fuel gas (a, b) and the presence or absence of CaO powder (b, c) It is a figure which evaluated the intermediate slag rate after desiliconization treatment by. The presence or absence of fuel gas when spraying refined dissolved oxygen gas and CaO powder onto the hot metal bath surface using a top-blown lance equipped with a burner function, and the total medial material used during desiliconization, dephosphorization, and decarburization treatment. It is a figure which shows the relationship with (CaO-containing powder) basic unit.

In the present invention, a refining method for performing desiliconization treatment, dephosphorization treatment and decarburization treatment using a single converter, particularly a medium-melting material which is a powder or granular material containing CaO used during refining, is in a state of a heat medium. This method is characterized in that it is supplied to the surface of hot metal or the like. As the configuration of the converter used in carrying out this refining method, the one shown in FIG. 1 is preferably used. That is, as shown in the figure, the converter uses a so-called one top-bottom blown converter capable of top-blowing oxygen gas and bottom-blowing gas for stirring hot metal. Moreover, this top-bottom blown converter is a top-blown with a burner that burns hydrocarbon-based fuel gas such as natural gas, city gas, propane gas, or vaporized liquid fuel in addition to oxygen gas and medial material through the top-blown lance. It is a furnace having a lance, and a combustion flame can be formed by burning a burner directly under the blown lance. Therefore, in the case of such a converter, when a medium-melting material made of powder or granular material containing CaO is passed through the top-blown lance, particularly the combustion flame due to the action of the burner, the medium-melting material is in the state of a heat medium. It will be sprayed into the molten iron, and high energy efficiency can be obtained.

Hereinafter, the converter refining method according to the present invention, which is carried out using the same top-bottom blown converter having the above equipment configuration, will be described.

Refining of the converter begins with charging iron scrap and hot metal into the upper bottom blowing converter, and then top blowing oxygen gas and a filler to perform desiliconization treatment.

In the desiliconization treatment, [Si] in the hot metal is oxidized by a part of the top-blown oxygen or the bottom-blown oxygen at the same time as the start of the blowing using the top-blown lance provided incidental to the converter. Then, it proceeds in the form of (SiO ₂ ) in the slag generated at this time (desiliconization treatment). The excess oxygen that was blown into the converter but was not consumed in this desiliconization treatment is used for decarburization by oxidation of [C] in the hot metal and for oxidation of iron in the hot metal, and is used in the slag (FeO). ) And transition. All of these oxidation reactions are exothermic reactions, and the heat of the reaction promotes the melting of iron scrap and at the same time raises the hot metal temperature.

In the present invention, as the desiliconization treatment progresses, the powder or granular material (medium-melting material) containing CaO heated by the combustion flame of the top-blown lance having a burner function and sprayed on the hot metal bath surface serves as a heat medium. Therefore, it quickly shifts into the slag in the form of (CaO). The basicity (CaO / SiO ₂ ) of the desiliconized slag generated in the furnace under such a reaction also changes depending on the dissolution rate of (CaO) and the formation rate of (SiO ₂ ). In addition, properties such as the melting point and viscosity of desiliconized slag vary greatly depending on the basicity and the composition ratio of other oxides in the slag such as (FeO). The basicity of these desiliconized slags and the ratio in the slag (FeO) are important operation control items for ensuring the fluidity of the slag in the intermediate slag after the desiliconization treatment. For example, if the basicity is too high or too low, the melting point and viscosity will increase. Therefore, it is preferable to adjust the slag basicity within the range of the desiliconization treatment temperature.

Therefore, the inventors have determined whether or not the hot metal bath surface in the converter is heated by blowing fuel gas from the top-blown lance, which affects the slag temperature when top-blown industrial oxygen gas or the like to desiliconize the hot metal. The effect of the presence or absence of CaO-containing powder or granular material, that is, CaO powder spraying was investigated. Specifically, it is equipped with a top-blowing lance that can blow industrial oxygen gas, CaO powder (medium-melting material) and burner combustion flame onto the molten iron bath surface, and a stirring gas is blown from the bottom-blowing tuyere at the bottom of the furnace. A test operation was carried out using a converter with a capacity of 300 tons, and the molten slag temperature and hot metal temperature during this operation were measured. The temperature of the molten slag and the hot metal was estimated from the change in thermoelectromotive force due to the thermocouple by attaching a temperature measuring probe to the tip of the sensor lance (sublance).

FIG. 1 shows a schematic view of the converter equipment used in this test, that is, the converter equipment equipped with a top-blown lance with a burner function. In FIG. 1, reference numeral 1 is an overall view of the converter equipment, 2 is the converter (main body), 3 is the top blown lance, 4 is the bottom blown tuyere, 5 is the hot metal, and 6 is the top blown lance. Oxygen gas jet, 7 is a CaO powder jet that passes through the combustion flame of a burner that uses natural gas as fuel, 8 is an oxygen gas supply pipe for supplying oxygen gas to the top blow lance, and 9 is to the top blow lance. A powder transport pipe for supplying CaO powder, 10 is a fuel gas supply pipe for supplying natural gas or the like to the top blow lance, and 11 is a cooling water supply pipe for supplying cooling water for cooling the top blow lance. , 12 are cooling water discharge pipes for discharging the cooling water that has cooled the top blown lance.

In the test using the converter, the top blown lance 3 is a rubberal type having 5 holes for refining nozzles installed at the tip thereof and an injection angle of 15 °. The top blowing lance 3 has a single-hole straight type powder blowing nozzle in the center, and has a burner function in which an annular fuel gas supply nozzle is arranged around the nozzle. In operation, the basic conditions are that the top-blown oxygen gas flow rate is 850 Nm ³ / min, the lance height is 3.0 m, and the bottom-blown gas flow rate is 50 Nm ³ / min, and when CaO powder is blown, the blowing speed is set. CaO powder or massive CaO was added from the upper part of the furnace so that the slag basicity at the end of the desiliconization treatment was 1.9 at 600 kg / min and 40 Nm ³ / min when natural gas was blown. Table 1 shows the specifications of the 5-hole Laval nozzle type injection nozzle having a burner function arranged on the top blowing lance 3. The injection angle (tilt angle) of the injection nozzle is a relative angle between the oxygen gas injection direction of the injection nozzle and the axial direction of the upper blowing lance.

In this test, the desiliconization treatment started from the time when the [Si] concentration in the hot metal was 0.3 mass% and continued until the time when the [Si] concentration in the hot metal reached 0.01 mass%. In addition, in order to investigate the difference in molten slag temperature depending on the presence or absence of a burner and the presence or absence of powder spraying,
(B) When natural gas is not supplied and only oxygen gas for refining and CaO powder are sprayed.
(B) When CaO powder is not sprayed and only oxygen gas for refining and natural gas are sprayed.
(C) When all of oxygen gas for refining, natural gas and CaO powder are sprayed
A comparative survey was conducted on the three levels.

FIG. 2 shows the temperature difference between the temperature of the molten slag and the temperature of the hot metal at the end of desiliconization at each level. “Projection of (a)” in FIG. 2 is a case where oxygen gas for refining and CaO powder are injected without injecting natural gas, and “(b) burner” in FIG. 2 is injection of CaO powder. Is a case where oxygen gas for refining and natural gas are injected without performing, and "(c) burner + projection" in FIG. 2 is a case where all of oxygen gas for refining, natural gas and CaO powder are injected. ..

As is clear from FIG. 2, the results show that the temperature of the molten slag is higher than the hot metal temperature at any level. Above all, the levels of (b) and (c) above are higher than the level of (a) (when only oxygen gas for refining and CaO powder are sprayed), and the temperature of the molten slag is higher than the level of (c). Burner projection) showed a remarkable effect of raising the temperature of the molten slag. In this case, the hot metal temperature at the end of desiliconization blowing was in the range of 1,300 ° C to 1,340 ° C at any level, so the molten slag temperature at the level (c) was about 1, It was found that the temperature reached 600 ° C or higher.

Next, an intermediate slag treatment was performed following the desiliconization treatment described above. The result is shown in FIG. The intermediate slag rate in FIG. 3 is a value defined by the following equation (1).

As is clear from FIG. 3, it was found that the intermediate slag rate (%) was improved at the level of high molten slag temperature (b) and (c) at the end of the desiliconization treatment.

Then, following the desiliconization treatment and the subsequent intermediate slag treatment, dephosphorization treatment and decarburization treatment were performed using the same converter. The top-blown lance used in these treatments has the same burner function as that used in the above-mentioned desiliconization treatment, and the top-blown oxygen gas flow rate is 1,200 Nm ³ / min, the lance height is 2.5 m, and the bottom is bottom. The flow rate of blown gas is 50 Nm ³ / min, the blowing speed of CaO powder is 600 kg / min, the amount of natural gas is 40 Nm ³ / min, the molten steel temperature at the end of dephosphorization and decarburization is 1,650 ° C. ] The amount of CaO powder blown and the amount of iron ore added were adjusted so that the concentration was 0.05 mass%, the [P] concentration in molten steel was 0.010 mass%, and the slag basicity was 3.5. The natural gas was stopped when the blowing of CaO powder was completed.

FIG. 4 shows the total amount of CaO basic units used in the desiliconization treatment, the dephosphorylation treatment, and the decarburization treatment under the top blowing conditions at the time of the desiliconization treatment, that is, natural gas is not supplied, and oxygen gas for refining and CaO powder are used. When (a), CaO powder is not sprayed, and oxygen gas for refining and natural gas are sprayed (b), when oxygen gas for refining, natural gas and all CaO powder are sprayed (c). This is a comparison of the three levels.

As a result, the total CaO basic unit used in the desiliconization treatment, the dephosphorylation treatment and the decarburization treatment decreased according to the intermediate slag rate after the desiliconization treatment. That is, it was found that the value was lowest when all the oxygen gas for refining, natural gas and CaO powder were sprayed from the top-blown lance during the desiliconization treatment (c).

Therefore, in the converter refining method according to the present invention, a fuel such as natural gas is added to the hot metal in the converter from the top-blown lance 3 to a filler material composed of powders and granules containing oxygen gas for refining and CaO powder. It can be seen that it is effective to inject the gas into the hot metal in the state of a heat medium by simultaneously injecting the gas and performing the desiliconization treatment. By performing such refining, the temperature of the molten slag during the desiliconization treatment can be raised, so that even if the composition of the medial material has a relatively high melting point, it can be reliably melted. As a result, the viscosity of the desiliconized slag is lowered and the dissolution range is expanded, and the slag efficiency at the time of intermediate slag can be improved.

This example is an example in which converter refining was performed using an upper bottom blowing converter (oxygen gas top blowing, stirring gas bottom blowing) as shown in FIG. 1 having a capacity of 300 tons. In this example, the refining nozzle installed at the tip of the top blowing lance 3 is a rubberal type with 5 holes and an injection angle of 15 °, and a single hole straight type powder blowing nozzle is in the center. An annular fuel gas supply nozzle was arranged around it, and a nozzle having a burner function was used. Refining the nozzle is obtained by equally spaced on the same circumference with respect to the axis of the top blowing lance, throat diameter (d _t) is 76.2 mm, out of the injection nozzle bore (d _e) is 80. It is 0 mm.

In the implementation, iron scrap was charged into the upper bottom blown converter, and then hot metal at 131 to 1360 ° C., which had been subjected to a desulfurization treatment in advance, was charged into the upper bottom blown converter. Next, from the bottom blowing tuyere 4, while blowing nitrogen gas into the hot metal as a stirring gas, the combustion flame of natural gas is blown from the top blowing lance 3 through the industrial oxygen gas, CaO powder and the burner to the hot metal bath surface. The desiliconization treatment was performed by spraying toward the furnace, and then the generated desiliconized slag was discharged to the outside of the furnace (intermediate discharge). Then, with a part of the desiliconized slag and the hot metal after the desiliconization treatment remaining in the furnace, argon gas is blown into the hot metal as a stirring gas from the bottom blowing tuyere 4 from the top blowing lance 3. Continued to spray industrial oxygen gas, natural gas and CaO powder toward the hot metal bath surface for dephosphorization and decarburization. Table 2 shows the chemical components of the hot metal used at this time, and Table 3 shows the conditions of top-blowing-bottom-blowing during desiliconization, dephosphorization, and decarburization.

Under such conditions, the [Si] concentration in the hot metal at the end of the desiliconization treatment is 0.01 mass%, the molten steel temperature at the end of the dephosphorization and decarburization treatment is 1650 ° C., and the [C] concentration in the molten steel is 0.04 mass%. The treatment time and the amount of iron ore added were adjusted so as to be.

In addition, a part of CaO added during the desiliconization treatment, dephosphorization and decarburization treatment is charged from the furnace hopper (not shown), and the rest is blown from the top blowing lance 3 to generate slag in the furnace. The total amount of addition was adjusted so that the basicity (mass% CaO / mass% SiO ₂ ) was 1.9 during the desiliconization treatment and 3.5 during the dephosphorylation and decarburization treatment.

Then, in order to maximize the heating effect of the slag in the furnace and obtain the effect of the present invention, the blowing of the natural gas for fuel and the CaO powder from the top blowing lance 3 is completely synchronized, and the blowing of the CaO powder is completed. At that point, the blowing of natural gas is also stopped, and the natural gas and CaO powder are blown from the top blowing lance 3 only during the desiliconization treatment in addition to the addition of the massive CaO from the hopper on the furnace (Example 1 of the present invention). However, natural gas and CaO powder were blown from the top-blown lance 3 in all the treatment steps of desiliconization, dephosphorization and decarburization (Example 2 of the present invention).

For comparison, the converter equipment and operating method follow the above-mentioned example of the present invention, but natural gas is not blown from the top-blown lance 3 and the massive CaO is formed from the top-blown hopper without forming a burner flame. An example (comparative example) in which only CaO powder was blown during desiliconization treatment, dephosphorization treatment, and decarburization treatment was also carried out in conjunction with the addition.
Below, Table 4 below shows the operating conditions and operating results in the above-mentioned examples of the present invention and the comparative examples.

As is clear from Table 4, the steelmaking time (time required from iron scrap charging to steel removal and completion of scavenging) was almost the same between the invention example and the comparative example, but in the comparative example, the present invention example The CaO basic unit increased and the iron yield decreased.
In this way, it was confirmed that by performing refining to which the method of the present invention is applied, it is possible to operate a converter that improves the iron yield and at the same time reduces the CaO basic unit.

1 converter equipment 2 converter (main body)
3 Top blown lance 4 Bottom blown tuyere 5 Hot metal 6 Oxygen gas jet 7 CaO powder jet 8 Oxygen gas supply pipe 9 Powder transport pipe 10 Fuel gas supply pipe 11 Cooling water supply pipe 12 Cooling water discharge pipe

Claims (2)

In the converter refining method for producing molten steel by performing dephosphorization treatment and decarburization treatment using the same converter, following the desiliconization treatment of hot metal and the subsequent intermediate slag treatment by the same converter , first, the converter After charging scrap and hot metal into the inside, an industrial oxygen gas is used for the desiliconization treatment performed by spraying a medial material composed of powders and granules containing industrial oxygen gas and CaO from a top-blown lance onto the hot metal bath surface. The desiliconization treatment is completed by heating the medium-melting material consisting of powder and granules containing CaO and CaO using a top-blown lance having a burner function to form a heat medium, and spraying it onto the hot metal or molten steel bath surface. converter refining method characterized by this that the intermediate Haikasu processing temperature of the desiliconization treatment slag at the time after the 1600 ° C. or higher. When producing molten steel by desiliconizing hot metal in the same converter and then performing dephosphorization and decarburization in the same converter following the subsequent intermediate slag treatment , first, scrap is placed in the converter. The hot metal is charged, and a medium melt material composed of powders and granules containing industrial oxygen gas and CaO is sprayed from the top-blown slag onto the hot metal bath surface to desiliconize the hot metal, and then after the desiliconization treatment. While a part of the slag is discharged to the outside of the furnace, an intermediate slag treatment is performed to make the inside of the furnace composed of the desiliconized hot metal and the residual amount of the slag after the desiliconization treatment, and then the desiliconization treatment is completed. The hot metal is dephosphorized and decarburized by spraying a medium-melting material consisting of powders and granules containing CaO together with oxygen gas for refining from the top-blown slag, and then dephosphorization and decarburization remaining in the furnace. In a converter refining method for producing molten steel by discharging the later molten steel to a molten steel pot and discharging part or all of the slag remaining in the furnace to the outside of the furnace after dephosphorization and decarburization.
In each of the desiliconization, dephosphorization, and decarburization treatments, a medial solution composed of powders and granules containing industrial oxygen gas and CaO is composed of powders and granules containing the CaO using a top blowing slag having a burner function. By heating the medial material to form a heat medium and spraying it onto the hot metal or molten steel bath surface, the desiliconization, dephosphorization and decarburization treatment slags are heated , and the desiliconization treatment is performed at the end of this treatment. A converter refining method, characterized in that the temperature of the desiliconized slag is set to 1600 ° C. or higher and then subjected to an intermediate waste treatment .

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