JP6237664B2 - Arc furnace operating method and molten steel manufacturing method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an arc furnace operating method for melting a cold iron source and a molten steel manufacturing method for manufacturing molten steel from a molten metal obtained by the arc furnace operating method.

  In an arc furnace, a cold iron source such as iron scrap is melted by arc heat, and then refined by a converter or the like to produce molten steel. The arc furnace facility consumes a large amount of electric power to generate arc heat. For the purpose of reducing this power consumption, melting the cold iron source by preheating the cold iron source using the exhaust gas generated from the melting chamber of the arc furnace during melting or increasing the carbon concentration in the molten metal A method has been proposed.

  Patent Document 1 uses an arc furnace including a melting chamber and a shaft-type preheating chamber that is directly connected to the melting chamber and into which exhaust gas generated in the melting chamber is introduced, and the cold iron source is the preheating chamber and the melting chamber. When the cold iron source in the melting chamber is heated by an arc while the cold iron source is melted by supplying the cold iron source to the preheating chamber, It has been proposed that the carbon concentration of the molten metal to be 1 mass% or more. In Patent Document 1, it is possible to increase the carbon concentration of the molten metal and lower the liquidus temperature (melting point) of the iron, thereby lowering the hot water temperature and melting the cold iron source with a small amount of electric power. Is described.

JP 2010-265485 A

  When steel material is manufactured by refining the molten metal obtained from the arc furnace in the next process equipment (converter, etc.), heat may be required in the refining process, and carbon in the molten metal is used as a heat source. In order to do so, a molten metal having a high carbon concentration may be required. In the invention described in Patent Document 1, although the carbon concentration in the molten metal can be increased, when the amount of slag increases on the molten metal in the melting chamber, the carbon material introduced into the melting chamber is blocked by the slag. Therefore, there is a possibility that a carbon material that does not dissolve in the molten metal is generated.

  The present invention has been made in view of the above problems, and the object of the present invention is to sufficiently utilize the carbonaceous material added to the molten metal when the molten metal is generated using a cold iron source and dissolve in the molten metal. An object of the present invention is to provide an arc furnace operating method capable of improving the amount of carbon (carbon yield).

The features of the present invention for solving such problems are as follows.
(1) A method of operating an arc furnace in which a cold iron source is charged into a melting chamber of an arc furnace having a melting chamber, and the cold iron source is melted by arc heating in the melting chamber. Operation of an arc furnace characterized in that carbon material is blown into the molten metal through a carbon material blowing immersion lance immersed in the molten metal generated by melting, and oxygen is blown into the slag generated on the molten metal. Method.
(2) A method for operating an arc furnace as described in (1) above, wherein a carbon material is blown into the slag.
(3) The arc furnace operating method according to the above (1) or (2), wherein a carbon material is charged toward the slag.
(4) The arc furnace operating method according to any one of (1) to (3), wherein the carbonaceous material is derived from biomass.
(5) A method for producing molten steel, characterized in that molten steel produced by the arc furnace operating method according to any one of (1) to (4) above is refined in a converter to obtain molten steel.

  According to the present invention, when manufacturing a molten metal using a cold iron source, the amount of carbon dissolved in the molten metal can be improved by fully utilizing the carbonaceous material added to the molten metal.

It is a vertical sectional view of an arc furnace facility. It is a vertical sectional view of an arc furnace facility of a form different from the arc furnace facility shown in FIG.

  The present invention uses an arc furnace having a melting chamber, inserts a cold iron source into the melting chamber and melts it by arc heating, thereby generating molten metal in the melting chamber, and charcoal in a state immersed in the molten metal. A carbon material is blown into the molten metal through a material blowing immersion lance, and oxygen is blown into the slag generated on the molten metal. By blowing the charcoal material directly into the molten metal from the carbon material blowing immersion lance, the carbonaceous material is dissolved in the molten metal without being blocked by the slag generated on the molten metal, and most of the amount of the blown carbon material is poured into the molten metal. This can contribute to the increased amount of dissolved carbon.

  When the amount of carbon dissolved in the molten metal is improved, the liquidus temperature (melting point) of iron in the molten metal is lowered and the temperature of the molten metal can be lowered, so that it is possible to rapidly dissolve with a small amount of power consumption. Furthermore, by blowing carbon directly into the molten metal and blowing oxygen into the slag, the carbon in the molten metal can be burned to heat the cold iron source and increase the temperature of the molten metal in a shorter time. The amount used can be further reduced.

  An example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of an embodiment of an arc furnace used in the practice of the present invention, and shows an arc furnace facility for adding a carbon material to a molten metal 17 through a carbon material blowing immersion lance 90 immersed in the molten metal. It is a vertical longitudinal cross-sectional view.

  The arc furnace 1 has a melting chamber 2 and a preheating chamber 3. The inner wall of the arc furnace 1 is constructed of a refractory, and a shaft-type preheating chamber 3 and a water-cooled furnace wall 4 are disposed on the upper part of the melting chamber 2 provided with the furnace bottom electrode 6 at the bottom. The upper opening of the furnace wall 4 that is not covered with 3 is covered with a furnace lid 5 having a water-cooling structure that can be freely opened and closed. An upper electrode 7 made of graphite that can move up and down into the melting chamber 2 through the furnace lid 5 is provided, and the base of the DC arc furnace 1 is configured. The furnace bottom electrode 6 and the upper electrode 7 are connected to a DC power source (not shown), and an arc 19 is generated between the furnace bottom electrode 6 and the upper electrode 7.

  Above the preheating chamber 3, a bottom-opening type supply bucket 13 suspended from the traveling carriage 24 is provided. From the supply bucket 13, an openable and closable supply port 20 provided at the top of the preheating chamber 3 is provided. Then, the cold iron source 15 is charged into the preheating chamber 3. A duct 21 provided at the upper end of the preheating chamber 3 is connected to a dust collector (not shown), and high-temperature exhaust gas generated in the melting chamber 2 is sucked through the preheating chamber 3 and the duct 21 in order, The cold iron source 15 is preheated. The preheated cold iron source 15 falls into the melting chamber 2 according to the amount of the cold iron source 15 to be melted in the melting chamber 2 and is charged into the melting chamber 2.

  The melting chamber 2 is provided with a carbon material blowing lance 90 and a carbon material blowing lance 9 that can move up and down while penetrating the furnace lid 5. The tip of the carbon material blowing immersion lance 90 is provided in the furnace lid 5 so that the tip thereof is immersed in the molten metal 17 generated as described later, and coke, char, coal, etc., using air or nitrogen as a carrier gas. Charcoal such as charcoal, graphite, biomass charcoal, or a mixture thereof is blown into the molten metal 17. The carbonaceous material is preferably derived from biomass. This is because coke contains sulfur (S), but it can prevent S contamination from the carbonaceous material by being derived from biomass. Furthermore, since biomass is carbon neutral, it is possible to reduce carbon dioxide emissions, which is one of the causes of global warming.

  In addition to the carbon material blowing lance 90 and the carbon material blowing lance 9, an oxygen blowing lance 8 that can move up and down while penetrating the furnace lid 5 is provided in the furnace lid 5. The oxygen blowing lance 8 is arranged so that the tip thereof is in contact with the slag 18 generated on the molten metal 17, and oxygen is blown into the slag 18 from the oxygen blowing lance 8.

  On the opposite side of the melting chamber 2 where the preheating chamber 3 is located, the outlet bottom 11 is pressed to the bottom of the furnace with a door 22 and filled with stuffed sand or mud agent. On the side wall, a door 23 is provided with a spout 12 which is pressed on the outlet side and filled with stuffed sand or mud agent. A burner 10 is attached to the furnace cover 5 at a position corresponding to the upper part of the steel outlet 11. The burner 10 burns fossil fuel and biomass fuel such as heavy oil, kerosene, pulverized coal, propane gas, and natural gas in the dissolution chamber 2 with air, oxygen, or oxygen-enriched air. The burner 10 can be removed as needed. When the molten metal 17 is discharged, the cold iron source 15 may not be dissolved. In this case, the cold iron source 15 and the molten metal 17 can be heated by the burner 10.

  In the operation of the arc furnace 1, first, the cold iron source 15 is charged into the preheating chamber 3 from the supply bucket 13. The cold iron source 15 charged into the preheating chamber 3 is also charged into the melting chamber 2, and eventually the preheating chamber 3 is filled with the cold iron source 15. In order to uniformly charge the cold iron source 15 into the melting chamber 2, the cold iron source 15 and the carbonaceous material are charged into the melting chamber 2 opposite to the preheating chamber 3 with the furnace lid 5 opened. Alternatively, hot metal may be charged into the melting chamber 2 when the cold iron source 15 is charged. By using hot metal, the amount of power used can be significantly reduced by the heat of the hot metal. Hot metal can be charged into the melting chamber 2 with a ladle for supply (not shown) or hot metal (not shown) connected to the melting chamber 2.

  Next, while feeding a direct current between the furnace bottom electrode 6 and the upper electrode 7, the upper electrode 7 is lowered, and between the furnace bottom electrode 6 and the upper electrode 7, or the inserted cold iron source 15 and The molten metal 17 is produced | generated by generating the arc 19 between the upper electrodes 7 and melt | dissolving the cold iron source 15 with arc heat. Then, molten slag (also simply referred to as “slag”) 18 is generated on the molten metal 17. If necessary, flux is added to the cold iron source 15, and the flux is melted to melt the molten slag 18. It may be generated. The molten metal 17 is kept warm by the molten slag 18. When the amount of the molten slag 18 is too large, the molten slag 18 can be discharged from the outlet 12 even during operation.

  After the energization, when the molten metal 17 and the molten slag 18 are formed, as shown in FIG. 1, the carbon material blowing immersion lance 90 is immersed in the molten metal 17, the carbon material is blown into the molten metal 17, and the oxygen blowing lance 8 is It is inserted into the molten slag 18 and oxygen is blown into the molten slag 18. Thereby, the carbon material directly blown into the molten metal 17 is dissolved in the molten metal 17, and the carbon concentration of the molten metal 17 is increased. In addition, oxygen blown into the slag reacts with carbon dissolved in the molten metal 17 to generate combustion heat, the temperature of the molten metal 17 rises, the melting of the cold iron source 15 is promoted, and thus power consumption is reduced. Can be suppressed.

The reaction product CO gas produced by the reaction of carbon in the molten metal 17 with oxygen forms the molten slag 18. Therefore, since the arc 19 is wrapped in the molten slag 18, the heat receiving efficiency of the arc 19 is increased. Further, the high-temperature CO gas generated in a large amount and the CO ₂ gas generated by combustion of this CO gas efficiently preheat the cold iron source 15 in the preheating chamber 3.

  In addition, it is preferable to blow oxygen into the molten slag 18 and blow carbon material into the molten slag 18 from the carbon material blowing lance 9. The oxygen blown into the molten slag 18 causes the charcoal material blown into the molten slag 18 to burn more actively than the charcoal material in the molten metal 17 to generate combustion heat, thereby improving the preheating efficiency of the cold iron source 15.

  As the cold iron source 15 in the melting chamber 2 melts, the cold iron source 15 in the preheating chamber 3 falls into the melting chamber 2 according to the amount dissolved in the melting chamber 2 and decreases. In order to compensate for this decrease, a cold iron source 15 may be inserted into the preheating chamber 3 from the supply bucket 13. The cold iron source 15 is charged into the preheating chamber 3 continuously or intermittently so that the cold iron source 15 is continuously present in the preheating chamber 3 and the melting chamber 2. In that case, it is preferable that the quantity of the cold iron source 15 which exists continuously in the preheating chamber 3 and the melting chamber 2 is 50 mass% or more of the amount of hot water discharged at one time. This is because if the amount of the cold iron source 15 continuously present in the preheating chamber 3 and the melting chamber 2 is reduced, the scrap preheating effect using the exhaust gas temperature is reduced.

  In this way, the cold iron source 15 and the molten metal 17 are heated to melt the cold iron source 15, the molten metal 17 is accumulated in the melting chamber 2, the carbon concentration of the molten metal 17 is measured, and if necessary, the oxygen blowing lance 8 Adjusting the carbon concentration (final target value) of the molten metal 17 to 1.0 mass% or more and 4.3 mass% or less by adjusting the oxygen blowing amount from the carbon and the carbon material blowing amount from the carbon material blowing immersion lance 90. preferable. Increasing the carbon concentration of the molten metal 17 has the effect of lowering the liquidus temperature (melting point) of iron. When the carbon concentration of the molten metal 17 is 1.0 mass% or more, the liquidus temperature (melting point) of iron is decreased. This is because the effect of lowering becomes prominent, the temperature of the hot water is lowered, and the cold iron source can be quickly dissolved with a small amount of power consumption. In addition, the carbon concentration of the molten metal 17 is set to 4.3 mass% or less. The liquidus temperature of iron continues to decrease until the carbon concentration is 4.3 mass%. This is because the liquidus temperature cannot be lowered.

The amount of oxygen blown into the molten slag 18 (Nm ³ / ton-molten metal) is preferably equal to or greater than the amount at which carbon of the carbonaceous material supplied to the molten slag 18 is completely combusted. If the oxygen blown into the molten slag 18 is completely consumed and all the carbon supplied to the molten slag 18 is combusted, the temperature of the molten metal 17 is increased efficiently. However, if oxygen is blown too much into the molten slag 18, the carbon dissolved in the molten metal 17 is actively burned, the carbon concentration in the molten metal 17 is lowered, and the liquidus temperature (melting point) of iron is hardly lowered. Become. Therefore, further, the oxygen amount (Nm ³ / ton-molten metal) blown into the molten slag 18 is the surplus carbon exceeding the final target concentration of carbon in the molten metal 17 and the carbon introduced into the molten slag 18. It is preferable to set the amount to be equal to or less than the amount for completely combusting both.

Considering the stoichiometric ratio in the reaction between carbon and oxygen, ideally, 1 (Nm ³ / ton-molten) of oxygen is about 1 (kg / ton-molten) of carbon to burn. Necessary. However, in the actual operation of the arc furnace 1, out of the total oxygen amount blown into the molten slag 18, the oxygen yield representing the proportion of the oxygen amount actually consumed for carbon combustion does not become 100%. Approximately 50%. This is because all the oxygen blown into the molten slag 18 due to gas leaking from the inside of the arc furnace 1 to the outside is not consumed for combustion. When the yield of oxygen is 50%, 2 (Nm ³ / ton-molten) of oxygen is required to burn 1 (kg / ton-molten) of carbon.

For example, when there is 180 tons of molten metal having a carbon concentration of 0.1% and the carbon concentration in the molten metal is increased to 4.1%, 7200 kg of carbonaceous material is added to the molten metal 17 (= 180 tons × 0.04). Will blow. Furthermore, for example, as much as 100 (kg / ton-molten) of carbon is blown into the molten metal 17 by the amount burned with oxygen, and 200 (Nm ³ / ton-molten) of oxygen is further blown into the molten slag 18. , 100 (kg / ton-molten) of the carbonaceous material is burned to form CO, and the temperature of the molten metal 17 rises. In addition, for example, both 100 (kg / ton / molten) of carbon material and 200 (Nm ³ / ton / molten) of oxygen may be blown into the molten slag 18 for burning with oxygen. Thereby, while aiming at the temperature rise of the molten metal 17 by the carbon combustion in the molten slag 18, the carbon concentration in the molten metal 17 can be kept high effectively, and the molten metal 17 can be made into the state in which liquidus temperature (melting | fusing point) fell. . Therefore, it is possible to melt the cold iron source 15 and discharge the molten metal 17 in a shorter operation time.

  When the target amount of the molten metal 17 is generated, the melting chamber 2 is tilted by a tilting device (not shown), and the molten metal 17 is discharged from the outlet 11. After pouring hot water, the molten slag 18 is discharged from the tap 12, and then the melting chamber 2 is returned to a horizontal position by a tilting device, and the pouring sand or mud material is filled in the tap 11 and the tap 12, The next melting of the cold iron source 15 is started.

  The discharged molten metal 17 is subjected to a refining process such as a desulfurization process for performing desulfurization, and then decarburized in a converter to obtain molten steel. Further, molten steel may be obtained by mixing at least a part of the molten metal from the arc furnace with the blast furnace hot metal and performing a desulfurization process in which desulfurization is performed, and performing a decarburization process in the converter.

  Next, an arc furnace 1 having a form different from that shown in FIG. 1 will be described with reference to FIG. FIG. 2 shows a case where the carbon material blowing lance 9 and the carbon material supply device 25 are used in combination when supplying the carbon material to the melting chamber 2. In the arc furnace 1 having the configuration shown in FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In the arc furnace 1 shown in FIG. 2, above the melting chamber 2, a hopper 26, a cutting device 28 provided at a lower portion of the hopper 26, an upper end thereof is connected to the cutting device 28, and a lower end thereof holds the furnace lid 5. A carbonaceous material supply device 25 configured with a supply chute 29 penetrating therethrough is installed.

  In the hopper 26, the same carbon material 27 as that used in the embodiment shown in FIG. 1 is stored, and the charging amount of the carbon material 27 is controlled by the cutting device 28 and melted through the supply chute 29. Can be put directly into chamber 2. By putting the carbon material 27 into the melting chamber 2 in this way, a carbon component that reacts with oxygen blown into the molten slag 18 is supplied. The charging amount of the carbon material 27 by charging from the hopper 26 can increase the charging amount of the carbon material per unit time as compared with the blowing amount by the carbon material blowing lance 9.

  The cold iron source 15 is mainly composed of iron such as iron scrap, iron scrap, directly reduced iron, and cold iron, and preferably contains a high carbon content cold iron source. In particular, when the cold iron source 15 includes a high carbon content cold iron source, the carbon concentration in the molten metal tends to increase. Therefore, the melting point of iron in the molten metal is lowered, and the temperature of the hot water can be easily lowered, so that the molten metal is easily melted quickly with a small amount of electric power used. The high carbon content cold iron source is a cold iron source having a carbon concentration of 1.0 mass% or more, for example, directly reduced iron (carbon concentration; 1 to 2 mass%) or cold iron (carbon concentration; 3 to 5 mass%). It is a cold iron source with a much higher carbon content than steel scrap mainly composed of steel with low carbon concentration. The cold iron is obtained by solidifying hot metal produced in a blast furnace, a smelting reduction furnace, or a cupola. Furthermore, since these high carbon content cold iron sources have few impure elements, it is also possible to dilute impurity elements such as Cu, Sn, and Cr caused by iron scrap.

  Although the case where the arc furnace 1 is a direct current type has been described in the above embodiment, the arc furnace 1 may be an alternating current type.

  By melting the cold iron source as described above, the molten metal having a high amount of dissolved carbon can be generated in order to use the carbon in the molten metal as a heat source used in the subsequent refining treatment.

  Using the arc furnace 1 shown in FIG. 2, the arc furnace that melts the cold iron source 15 to generate the molten metal 17 was operated. The melting chamber 2 has a furnace diameter of 7.2 m and a height of 4 m, and the preheating chamber 3 has a width of 3 m, a length of 5 m, a height of 7 m, and a furnace capacity of 180 tons. Iron scrap was used as the cold iron source 15 and coke was used as the carbonaceous material.

First, about 70 tons of normal-temperature iron scrap is charged into the preheating chamber 3, then 50 tons of normal-temperature iron scrap and 1 ton of coke are charged into the melting chamber 2, and a graphite upper electrode having a diameter of 30 inches. 7 was used to start melting iron scrap using a power source with a maximum capacity of 750 V and a maximum capacity of 130 KA, and a molten metal 17 was generated. The voltage at this time was set to 550V. Immediately after energization, iron scrap was added to quicklime and fluorite. The quicklime and fluorite were heated to form molten slag 18, and oxygen was blown into the molten slag 18 on the molten metal 17 from the oxygen blowing lance 8, and coke was blown into the molten metal 17 from the carbon material blowing immersion lance 90. The oxygen gas blowing amount from the oxygen blowing lance 8 was 15 (Nm ³ / ton-molten metal), and the carbon material blowing amount (carbon material amount) was 52 (kg / ton-molten metal). In the operation of the arc furnace 1 in the present embodiment, the oxygen yield representing the proportion of the oxygen amount actually consumed for carbon combustion out of the total oxygen amount blown into the molten slag 18 is about 50%.

  After that, when the iron scrap in the preheating chamber descends as it melts, the iron scrap is charged into the preheating chamber with the supply bucket, and continues to melt while maintaining the iron scrap height in the preheating chamber at a constant height, and When 140 tons or more of molten metal was generated in the melting chamber, 140 tons of molten metal was discharged into a ladle. After pouring, the iron scrap was again charged into the preheating chamber and the melting chamber and melted in the same manner as described above to generate molten metal. When the amount of molten metal reached 140 tons or more, 140 tons of hot water was discharged again. The total amount of molten metal after tapping is 280 tons (Invention Example 1).

  The molten metal 17 is generated in the arc furnace 1 in the same manner as in Example 1 of the invention except that the amount of carbon material blown from the carbon material blowing immersion lance 90 and the final target concentration of carbon in the molten metal 17 (the hot water C concentration) are changed. (Invention Examples 2 and 3).

  The amount of carbon material blown from the carbon material blowing lance 90 is changed and the carbon material is supplied from the carbon material blowing lance 9 to the melting chamber 2 or from both the carbon material blowing lance 9 and the carbon material supply device 25. The molten metal 17 was produced | generated by the arc furnace 1 like this invention example 1 except having supplied the carbon material to the melting chamber 2 (this invention example 4 and 5).

Other than supplying the carbon material from both the carbon material supply device 25 and the carbon material blowing lance 9 and changing the amount of blowing the carbon material from the carbon material blowing immersion lance 90 and the oxygen gas blowing amount blown from the oxygen blowing lance 8 Produced the molten metal 17 in the arc furnace 1 in the same manner as in Invention Example 1 (Invention Example 6). In Example 6 of the present invention, the oxygen gas blowing amount (Nm ³ / ton-molten metal) is equal to or greater than the amount that completely burns carbon of the carbon material supplied to the molten slag 18, and the tapping C concentration is 4.1 mass%. There is a surplus of carbon beyond that amount to burn. In the present invention example 6, oxygen blown into the molten slag 18 is completely consumed, a part of the carbon in the molten metal 17 and the carbon supplied to the molten slag 18 are all burned, and the molten metal 17 is heated. become.

  The molten metal 17 was produced | generated by the arc furnace 1 like this invention example 1 except the charcoal material from the carbon material blowing immersion lance 90 being coconut shell (PKS) charcoal instead of coke (Invention example 7).

  Next, in order to compare with Examples 1 to 7 of the present invention, the carbon material from the carbon material blowing immersion lance 90 is not blown into the molten metal 17, and the carbon material is dissolved from the carbon material blowing lance 9 and the carbon material supply device 25 into the melting chamber 2. The molten metal 17 was produced | generated by the arc furnace 1 like this invention example 1 except having added to (comparative example).

  Table 1 shows the operating conditions and results of Examples 1 to 7 of the present invention and Comparative Examples.

  The “carbon material yield (−)” shown in Table 1 means the amount of carbon in the molten metal 17 relative to the amount of carbon material blown into the melting chamber 2 and / or the molten metal 17, and the carbon concentration in the molten metal 17 is fluorescent. Measurement was performed using an X-ray apparatus. The “tap-tap time” is the time from the start of hot water to the next start of hot water. The smaller this time, the more efficiently the cold iron source 15 was melted in the arc furnace 1 from the viewpoint of time. The “power intensity” is, for example, a value (kWh / ton-molten metal) obtained by dividing the amount of power (kWh) required to generate a molten metal of 280 tons by 280 tons.

  In Invention Example 1, Invention Examples 4 to 7 and Comparative Example, the tapping C concentration is the same value as 4.1 mass%. From Table 1, it is possible to confirm how the time taken to set the amount of carbon dissolved in the molten metal, the electric power consumption unit and the concentration of discharged hot water C as target values in an operation with the same hot water C concentration changes. In Invention Examples 2 and 3, the hot water C concentration is not 4.1 mass%, but in comparison with Invention Example 1, by changing the amount of carbon material blown from the carbon material blowing immersion lance 90, You can see how the amount of dissolved carbon changes.

  In the present invention examples 1 to 7, since the carbon material is directly blown into the molten metal from the carbon material blowing immersion lance, the carbon material is not blocked by the slag, and the carbon material yield can be increased as compared with the comparative example. . First, in Example 1 of the present invention, the carbonaceous material yield can be increased as compared with the comparative example. Since the carbonaceous material added to the melting chamber (molten metal) is not blocked by the slag, it can be seen that the carbonaceous material was fully utilized and efficiently dissolved in the molten metal. Therefore, the amount of charcoal material can be reduced as compared with the comparative example having the same hot water C concentration. In addition, the amount of power can be reduced and the tap-tap time can be shortened as compared with the comparative example because the carbon material can be efficiently dissolved in the molten metal.

  In Invention Examples 2 and 3, the concentration of tapping hot water C is lower than that of Invention Example 1, and the amount of carbon material is small. In particular, in Invention Example 3, the concentration of tapping water C is low, so the liquidus temperature is high and the tapping temperature is high. In addition, the tap-tap time and the power consumption rate are deteriorating. However, in both of the present invention examples 2 and 3, the carbon material is directly blown into the molten metal from the carbon material blowing immersion lance 90, the carbon material yield is improved as compared with the comparative example, and the carbon material is efficiently dissolved in the molten metal. Is able to.

  In Invention Examples 4 and 5, the carbonaceous material yield can be increased as compared to the comparative example, and the total amount of the carbonaceous material supplied to the melting chamber can be less than that of the comparative example having the same tapping C concentration. Yes. Furthermore, by actively burning the carbonaceous material added to the molten slag 18, the basic unit of electric power can be reduced and the tap-tap time can be shortened.

  In Example 6 of the present invention, an amount of carbon material that is equal to or higher than the target concentration (4.1 mass) of carbon is blown directly into the molten metal 17 and the carbon material is supplied to the molten slag 18 and the carbon material supplied to the molten slag 18 An amount of oxygen that burns all of the carbonaceous material in an amount that is equal to or higher than the target concentration is blown into the molten slag 18. Thereby, in Invention Example 6, compared with Invention Examples 1 to 5, carbon combustion is promoted in the molten slag 18 and the molten metal 17, and the power unit is reduced and the tap-tap time is greatly increased. It can be seen that the carbon material was efficiently dissolved in the molten metal 17 from the viewpoint of time.

  In Invention Example 7, it can be seen that compared with Invention Example 1, the concentration of discharged hot water S is suppressed.

  In the method for operating an arc furnace according to the present invention, in order to use the carbon in the molten metal as a heat source used in the subsequent refining treatment, the molten carbon has a higher amount of dissolved carbon than the amount of supplied carbon. It turns out that was able to be generated. In addition, it can be seen that by adjusting the amount of oxygen blown into the slag and the amount of carbon supplied to the slag, it was possible to improve the productivity of the molten metal and reduce the power consumption.

DESCRIPTION OF SYMBOLS 1 Arc furnace 2 Melting chamber 3 Preheating chamber 4 Furnace wall 5 Furnace lid 6 Furnace bottom electrode 7 Upper electrode 8 Oxygen blowing lance 9 Carbon material blowing lance 10 Burner 11 Steel outlet 12 Steel outlet 13 Supply bucket 15 Cold iron source 17 Molten metal 18 Molten slag (slag)
19 Arc 20 Supply port 21 Duct 22 Door 23 Door 24 Traveling carriage 25 Charcoal material supply device 26 Hopper 27 Carbon material 28 Cutting device 29 Supply chute 90 Carbon material blowing immersion lance

Claims (4)

A method of operating an arc furnace in which a cold iron source is charged into a melting chamber of an arc furnace having a melting chamber, and the cold iron source is melted by arc heating in the melting chamber,
While blowing the carbonaceous material into the molten metal through the carbonaceous material blowing immersion lance immersed in the molten metal generated by melting the cold iron source,
An operating method for an arc furnace, characterized in that oxygen and a carbon material are blown into the slag produced on the molten metal so that the amount of the blown oxygen is equal to or greater than the amount of carbon of the carbon material blown into the slag . The operation method of the arc furnace according to claim 1, wherein charcoal is introduced toward the slag. The method for operating an arc furnace according to claim 1 or 2 , wherein the carbonaceous material is derived from biomass. A method for producing molten steel, comprising obtaining a molten steel by refining a molten metal produced by the method for operating an arc furnace according to any one of claims 1 to 3 in a converter.

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