JP6398582B2 - Powder blowing lance device, powder blowing method, and converter refining method - Google Patents

Description

  The present invention uses a powder blowing lance device for blowing powder together with oxygen gas to a molten metal in a converter, a powder blowing method using the same, and a converter having the powder blowing lance device. It relates to the converter refining method.

  Conventionally, in steel refining using a converter, a method of performing both dephosphorization and decarburization refining by one refining of hot metal charged in the converter has been used. In recent years, many methods have been used in which hot metal dephosphorization is first performed as a hot metal preliminary treatment, and then decarburization is performed in a converter. Recently, converters are increasingly used as refining furnaces to perform hot metal pretreatment in terms of reaction efficiency.

  When performing dephosphorization refining in a converter, dephosphorization slag and molten iron produced after dephosphorization are separated, and then decarburization refining is performed in the converter. As a method for separating dephosphorization slag, the molten iron is discharged from the steel outlet of the converter where the dephosphorization and refining was performed, the slag is discharged, and the molten iron is charged into a different converter and decarburized and refined ( (Hereinafter also referred to as “the separate converter method”), and after dephosphorization and refining, the converter is tilted while leaving the molten iron in the converter, and only the slag is discharged from the furnace port, and then decarburization and refining in the same converter. One of the methods (hereinafter also referred to as “same converter method”) is used. The same converter method is preferable as compared with the separate converter method because there is no need for tapping and recharging, so the productivity of the converter is not reduced and the heat loss due to the transfer of molten iron is small.

  In converter refining, an upper bottom blowing converter in which oxygen gas is blown from the top blowing lance to the molten metal in the converter and gas is also blown from the bottom of the converter in recent years is mainly used.

  Patent Document 1 discloses a refining method in a top-bottom blown converter, in which a powdery flux for slagging is accompanied by an oxygen jet sprayed from the top blowing lance to the surface of the molten iron, and the refining is performed by spraying the molten iron on the molten iron. Yes. According to the embodiment, molten iron is charged into the converter, desiliconization, dephosphorization, and decarburization refining are performed at once, and from the top blowing lance with oxygen from the top blowing lance during the period of 15-20 minutes from the beginning of blowing. Continuously spraying quicklime powder.

  In Patent Document 2, when performing desiliconization and dephosphorization processing of hot metal using a converter type hot metal pretreatment furnace, a method of spraying together with top blowing oxygen using a fine powder CaO source, and a bottom blowing tuyere It is disclosed that a method of blowing a CaO source is used in combination.

  Patent Document 3 discloses a refining method using an upper blowing lance equipped with a nozzle capable of separately blowing main refining oxygen, a powder refining agent, and secondary refining oxygen as an upper blowing lance. Has been. Refinement is carried out by blowing fine powdery lime-forming agent from the central nozzle (powder-making agent nozzle), and stirring gas is blown from the bottom blowing nozzle. The main refining oxygen nozzle and the secondary refining oxygen nozzle are arranged around the powder forming agent nozzle in the center.

  When refining in a converter, the converter furnace mouth is turned upward, the top blowing lance is lowered from the furnace mouth, the tip of the lance is placed near the molten metal surface, and oxygen top blowing is performed. Since the converter is tilted during hot metal charging and steel removal, the lance is raised. A lance lifting device is used for lifting the lance. The lance lifting device includes a lifting guide device and a lifting platform, the lifting platform can be moved up and down along the lifting guide device, and the lance is attached to the lifting platform. Regarding the supply of oxygen gas to the lance, a flexible hose for oxygen is used in order to cope with the raising and lowering of the lance. Connect the oxygen flexible hose with the connection port to the lance facing up and the connection port with the lance hose facing down. In order to direct the connection port to the hose of the lance downward, a U-shaped pipe for oxygen circulation is arranged at the upper end of the lance (see Non-Patent Document 1).

  The lance may be replaced for lance nozzle repair or operational reasons. In order to replace the lance quickly, two sets of lance lifting devices may be arranged in one converter. Two sets of lance lifting devices are traversed to move back and forth between the operation position and the standby position (see Non-Patent Document 2). At the standby position, after cutting off the cut-off portion of the oxygen gas flow path, the lance is lifted with a hoist crane or the like, removed from the lifting platform, and the lance is replaced. Place a new lance on the lifting platform and connect the disconnected part of the oxygen gas flow path. At the upper end of the lance, a frame for lifting with a hoist crane is disposed (see Non-Patent Document 2, page 461, FIGS. 8 and 42). By hanging a hoist crane hook on the frame, the lance can be lifted and lowered separately from the lifting rack.

Japanese Patent Laid-Open No. 58-19423 JP 2010-150574 A (Japanese Patent No. 5386972) JP 60-56009 A

Japan Iron and Steel Institute “Oxygen Steelmaking History in Japan” page 185 Japan Iron and Steel Institute, 3rd edition Steel Handbook II Steelmaking and Steelmaking, page 461

  In order to spray powder together with oxygen gas to the molten metal in the converter, it is necessary to join the powder to the oxygen gas flow path in the vicinity of the upper end of the lance. In order to transport the powder to the vicinity of the upper end of the lance, the oxygen gas is supplied to the vicinity of the upper end of the lance with the flexible hose for powder together with the carrier gas in the same manner as oxygen gas is supplied to the vicinity of the upper end of the lance by the flexible hose for oxygen. The powder conveyance path further extends from the tip of the powder flexible hose and merges with the oxygen gas flow path at the merge position. The carrier gas and the powder supplied by the flexible hose for powder merge with the oxygen gas at the joining position, and are thereafter conveyed to the oxygen gas. The oxygen gas, powder, and carrier gas are transferred to the molten metal from the nozzle at the lower end of the lance. It spouts towards.

  In converter refining, various varieties are melted for each charge. Even in a converter having a function of spraying powder together with oxygen gas from an upper blowing lance, there are cases where a variety of types in which powder is sprayed and a variety in which powder is not sprayed are mixed. When refining varieties that are not sprayed with powder, the carrier gas and powder are not supplied to the powder transport path, while the oxygen gas flow path has a pressure higher than normal pressure (hereinafter referred to as “high pressure”). Oxygen gas may be supplied. Therefore, oxygen gas enters the powder conveyance path at the joining position of the powder conveyance path and the oxygen gas flow path, and high-pressure oxygen gas enters the flexible hose for powder. That is, even when powder blowing is not performed, the powdered flexible hose is subject to the internal pressure of high-pressure oxygen gas, so that the lifetime of the powdered flexible hose is shortened.

  The present invention relates to a powder blowing lance device for blowing powder together with oxygen gas to molten metal in a converter, and can be used to protect a flexible hose for powder during refining without performing powder blowing. An object is to provide a lance device.

That is, the gist of the present invention is as follows.
(1) A powder blowing lance device for blowing powder together with oxygen gas to the molten metal in the converter. The lance lifting device for lifting the lance includes a lifting guide device and a lifting platform, and the lifting platform is lifted and lowered. It can be moved up and down along the guide device, and the lance is attached to the lifting platform.
Oxygen gas is sent to the lifting platform by an oxygen flexible hose, and the oxygen gas flow path is bent into a U-shape through the oxygen flow path disconnecting part for exchanging the lance, and enters the lance from the upper end of the lance. Supplied,
The powder is sent to the lifting platform together with the carrier gas by the flexible hose for powder, and the powder transportation path is a U-shaped oxygen gas channel through the powder channel separation part for lance replacement on the lifting platform . After joining the curved pipe , the powder is blown along with oxygen gas to the molten metal in the converter via all nozzles at the bottom of the lance,
A powder blowing lance device comprising a shut-off valve (hereinafter referred to as “end valve”) in the middle of a powder conveyance path on a lifting platform and upstream of the separation portion.
(2) at a position where the powder transport path from entering the curved pipe portion of the U-shaped oxygen gas channel, the powder transport path enters the oxygen gas flow path with an inclination angle to the vertical, U-shaped In at least a part of the bent portion of the oxygen gas flow path, the oxygen gas flow path and the powder conveyance path have a double pipe shape, and the powder is directly perpendicular from the end of the inner pipe of the double pipe. The powder blowing lance device according to (1) above , wherein an inner tube is disposed so as to be introduced into the lance.
(3) In the middle of the powder conveyance path, an upstream shut-off valve is provided upstream of the powder flexible hose, and a pressure release valve is provided between the upstream shut-off valve and the end valve. The powder blowing lance device according to the above (1) or (2).
(4) A powder blowing method using the powder blowing lance device according to the above (1) or (2), wherein the end valve is closed at the time of blowing only oxygen gas without blowing powder from the tip of the lance. The powder blowing method is characterized in that the end valve is opened when oxygen gas is blown together with powder from the tip of the lance.
(5) A powder blowing method using the powder blowing lance device as described in (3) above, wherein the terminal valve and the upstream shut-off valve are closed when only oxygen gas is blown without blowing powder from the tip of the lance. And a pressure blowing valve, wherein at the time when oxygen gas is blown together with powder from the tip of the lance, the terminal valve and the upstream shut-off valve are opened and the pressure relief valve is closed.
(6) above (1) to (3) of a any one converter refining method using a converter having a powder blowing lance according to, first the molten iron was charged into a converter dephosphorization When refining and discharging molten slag from the converter furnace port while leaving the molten metal in the converter after dephosphorization refining, and then performing decarburization refining, the powder together with oxygen gas from the lance during the dephosphorization refining A converter refining method characterized in that, in the initial stage of the decarburization refining, powder is blown together with oxygen gas from the lance, and in the final stage of the decarburization refining, only oxygen gas is blown without blowing powder from the lance. .

  The present invention relates to a powder blowing lance device for blowing powder together with oxygen gas to a molten metal in a converter, the lance is attached to an elevating base and moves up and down, and the powder conveyance path is a U-shaped oxygen gas A shut-off valve (end valve) is provided in the middle of the powder conveyance path on the lifting platform and on the upstream side of the powder flow path separating portion. As a result, when oxygen gas is blown from the top blowing lance to the molten metal during blowing, but the powder is not sprayed, the pressure of the high pressure oxygen gas is not applied to the powder flexible hose by blocking the end valve. It is possible to extend the life of the body flexible hose.

It is a figure which shows the part on the lifting stand of the powder blowing lance apparatus of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram which shows the whole powder blowing lance apparatus of this invention, (a) is a figure in which a lance is located in a raise upper limit, (b) is a figure which shows the condition where the lance is falling to the blowing position. is there. It is a fragmentary sectional view showing a part of the powder blowing lance device of the present invention.

  The present invention will be described with reference to FIGS.

  As shown in FIG. 2, the powder sprayed together with oxygen gas from the nozzle 3 located at the tip of the upper blowing lance 2 is supplied from a powder supply device 19. In the powder supply device 19, the powder is stored in the blowing tank 20, conveyed to the carrier gas via the feeder 21 below the blowing tank, and moves in the piping of the powder conveying path 32. The powder conveyance path 32 passes through the powder flexible hose 15 and joins the oxygen gas flow path 31 at the joining portion 17 near the upper end of the lance. During oxygen blowing, the pressure in the oxygen gas flow path near the upper end of the lance is, for example, a high pressure of less than 1 MPa, so the transport gas pressure in the powder transport path is also a high pressure commensurate with it.

  When powder blowing is not performed during oxygen blowing, the carrier gas supply from the powder feeder 19 is not performed, so the carrier gas pressure in the powder carrier path is reduced. At this time, the high-pressure oxygen gas flows backward from the joining position of the oxygen gas flow path 31 and the powder conveyance path 32 to the powder conveyance path 32, so that the oxygen gas does not flow back to the powder supply device 19. A shut-off valve (upstream shut-off valve 18) is provided on the upstream side of the powder flexible hose in the body conveyance path 32. At the timing when the powder is not transported, the upstream shut-off valve 18 is closed to prevent the backflow of oxygen gas. The upstream shut-off valve 18 is also called a backflow prevention valve.

  When powder blowing is not performed during oxygen blowing, the upstream shut-off valve 18 is closed, so that high-pressure oxygen gas does not stay on the upstream side of the upstream shut-off valve 18. However, high-pressure oxygen gas stays in the powder flexible hose 15 on the downstream side of the upstream shut-off valve 18 and the internal pressure is continuously applied to the flexible hose.

  In the present invention, the lance elevating device 4 for elevating and lowering the lance includes an elevating guide device 5 and an elevating frame 6, the elevating frame 6 can be moved up and down along the elevating guide device 5, and the lance 2 is attached to the elevating frame 6. Yes. Oxygen gas is sent to the lifting platform 6 by the oxygen flexible hose 11, and the oxygen gas channel 31 on the lifting platform 6 passes through the oxygen channel disconnecting portion 12 for lance replacement and is bent into a U shape. It is fed into the lance 2 from the lance upper end 14 via the character-shaped portion 13. When exchanging the lance, the oxygen flow path disconnecting portion 12 is disconnected, and then the lance 2 is lifted by a hoist crane or the like and removed from the lifting platform 6 to replace the lance.

  In order to spray the powder from the upper blowing lance, the powder is sent to the lifting platform 6 via the powder flexible hose 15 together with the carrier gas. The powder conveyance path 32 also has a powder flow path separating portion 16 for exchanging lances on the lifting platform. At the time of lance replacement, the lance replacement is performed after the powder flow path disconnecting portion 16 is also disconnected. The powder conveyance path 32 is joined to the U-shaped oxygen gas flow path 31 through the powder flow path separating portion 16, and the powder is transferred to the molten metal in the converter 1 through the nozzle 3 at the lower end of the lance together with the oxygen gas. Be sprayed.

  In the powder blowing lance device of the present invention, as shown in FIG. 1, a shut-off valve (end valve 7) is provided in the middle of the powder conveyance path 32 on the lifting platform 6 and upstream of the powder flow path separating portion 16. ). Since the end valve 7 is provided in the middle of the powder conveyance path 32 on the lifting platform, it is on the downstream side of the powder flexible hose 15. Therefore, when oxygen powder is blown from the top blowing lance 2 to the molten metal during blowing, but the powder is not sprayed, the pressure of the high-pressure oxygen gas is not applied to the powder flexible hose 15 by blocking the end valve 7. It becomes.

  In the powder conveyance path 32 of the present invention, it is further preferable to provide a pressure relief valve 9 between the upstream shut-off valve 18 and the end valve 7 as shown in FIG. When the powder is not blown, the internal pressure of the powder flexible hose 15 is made normal by releasing the pressure relief valve 9 after shutting off both the upstream side shut-off valve 18 and the end valve 7. Thus, the life of the powdered flexible hose 15 can be further extended.

  It is necessary to install a control cable for operating the end valve 7 of the present invention. If the end valve 7 is provided on the downstream side of the powder flow path disconnecting portion 16 in the powder conveyance path 32, the end valve 7 is disposed on the side where the end valve 7 is disconnected together with the lance 2 when replacing the lance. The control cable 7 is also required to be disconnected, which is not preferable because the work becomes complicated. Moreover, since it is necessary to provide end valves for all the lances to be used, it is uneconomical. In the present invention, this problem is solved by providing the end valve 7 in the middle of the powder conveyance path 32 on the lifting platform and on the upstream side of the powder flow path separating portion 16. Even at the time of exchanging the lance, the end valve 7 remains fixed on the lifting platform 6, so there is no need to disconnect the control cable of the end valve 7. Further, it is economical because it is sufficient to provide a terminal valve for each lance lifting platform.

  The oxygen gas flow path 31 of the lance device is sent to the lift frame 6 via the oxygen flexible hose 11 as described above, and the oxygen gas flow path 31 is separated from the oxygen flow path for lance replacement on the lift frame. The lance 2 is supplied vertically from the upper end 14 of the lance via the U-shaped portion 13 bent into a U-shape through the portion 12. When the powder blowing path is joined to the oxygen gas flow path 31, it is advantageous if the powder and the carrier gas can also join the lance vertically in a portion where the oxygen gas is vertically guided into the lance. However, as described above, a bracket 22 for lifting the lance with a hoist crane is disposed immediately above the lance 2 (FIG. 1). When trying to join the powder vertically to the lance, the powder supply path interferes with this frame. If the position of the frame is changed further upward, the position of the hoist crane needs to be changed upward, and the converter height of the converter factory needs to be increased, which is not realistic.

  In the present invention, as shown in FIG. 1, the powder conveyance path 32 has an inclination angle θ with respect to the vertical, as shown in FIG. 1, with respect to the junction 17 where the powder conveyance path enters the U-shaped oxygen gas flow path. The above-mentioned problem was solved by arranging so as to enter the road 31. Since the powder conveyance path 32 is inclined, it is possible to install the powder conveyance path 32 while avoiding the position of the bracket 22 arranged immediately above the lance. The inclination angle θ with respect to the vertical is preferably about 40 degrees or more because the problem can be avoided more reliably. 1 and 3, the inclination angle θ with respect to the vertical is 45 degrees.

  A copper pipe is used as the material of the U-shaped portion 13 bent into the U-shape of the oxygen flow path. The reason why the copper pipe is used as the material is that it is suitable for the purpose of preventing ignition and fire spread because pure oxygen gas flows inside. If the powder collides with the inner wall of the U-shaped portion 13 after the powder is merged into the oxygen gas, it is not preferable because the copper tube is worn. As described above, when the powder conveyance path 32 is arranged so as to enter the merging portion 17 of the oxygen gas flow path with an inclination angle θ with respect to the vertical, the merged powder collides with the copper tube of the U-shaped portion 13 as it is. There are concerns. Therefore, the present invention solves this problem by assuming that the oxygen gas flow path 31 and the powder conveyance path 32 have a double-pipe configuration in at least a part of the U-shaped oxygen gas flow path. When the oxygen gas flow path 31 is an outer tube, the powder transport path 32 is the inner tube 8. Even if the powder conveyance path 32 joins the oxygen gas flow path 31, if it is in the form of a double pipe, the powder will collide only with the inner wall of the inner pipe 8 in the double pipe region, Since it does not collide with the inner wall of the formed outer tube, wear of the copper tube can be prevented. Then, the end portion of the inner tube 8 of the double tube is opened, and the powder discharged from the inner tube together with the carrier gas is introduced into the vertical lance 2 without colliding with the inner wall of the U-shaped copper tube. It is preferable to arrange the inner tube 8 as described above. Furthermore, as shown in FIG. 3, it is more preferable that the end portion of the inner tube 8 is directed vertically downward because the powder does not collide with the inner wall of the lance even in the lance. About the inner surface of the inner tube 8 of the double tube, for example, ceramics can be used to prevent wear due to powder blowing.

  In the powder blowing lance device for blowing powder together with oxygen gas, as described above, a shut-off valve (upstream shut-off valve 18) is provided on the upstream side of the powder flexible hose 15 in the powder transport path 32 (FIG. 2). reference). At the timing when the powder is not transported, the upstream shut-off valve 18 is closed to prevent the backflow of oxygen gas. As described above, the present invention includes a shut-off valve (terminal valve 7) in the middle of the powder conveyance path on the lifting platform. The end valve 7 is located downstream of the powder flexible hose 15. The present invention preferably further includes a pressure relief valve 9 between the upstream shut-off valve 18 and the end valve 7, as shown in FIG. At the timing when oxygen gas is blown into the converter but no powder is blown, both the upstream shut-off valve 18 and the end valve 7 are closed, and the pressure relief valve 9 is opened, whereby the powder flexible hose 15 is opened. The pressure on the hose can be reduced by reducing the internal and external pressure difference of the flexible hose for powder.

  The powder blowing method using the powder blowing lance device of the present invention will be described. In the case of using the powder blowing lance device of the present invention, a mode in which both pure oxygen gas and powder are blown from the nozzle 3 at the tip of the lance, and a mode in which only pure oxygen gas is blown from the tip of the lance and no powder blowing is involved. You can switch freely. Specifically, a shut-off valve (end valve 7) is provided in the middle of the powder conveyance path 32 on the lifting platform and on the upstream side of the powder flow path separating portion 16, so that powder is not blown from the tip of the lance. When the oxygen gas alone is blown, the end valve 7 is closed, and when the oxygen gas is blown together with the powder from the tip of the lance, the end valve 7 is opened to switch between the two modes. In the case of blowing oxygen gas from the top blowing lance 2 to the molten metal during blowing, if the powder is not blown, the pressure of the high-pressure oxygen gas is not applied to the powder flexible hose 15 by blocking the end valve 7. . As a result, the lifetime of the powder-use flexible hose 15 can be sufficiently maintained.

  Further, when using a powder blowing lance device having a pressure relief valve between the upstream shutoff valve and the end valve, the upstream shutoff from the end valve 7 is performed when only oxygen gas is blown from the tip of the lance. When the valve 18 is closed and the pressure relief valve 9 is released and oxygen gas is blown together with powder from the tip of the lance, the terminal valve 7 and the upstream shut-off valve 18 are opened and the pressure relief valve 9 is closed to blow the powder. When this is not performed, the internal pressure of the powder flexible hose 15 can be made normal, and the life of the powder flexible hose can be further extended.

  When dephosphorization and decarburization are separated and dephosphorization is performed in the converter, as described above, slag is discharged after discharging molten iron from the outlet of the converter where dephosphorization was performed. , Decarburizing and refining by charging molten iron into different converters (separate converter method), and tilting the converter while leaving the molten iron in the converter after dephosphorization and removing only slag from the furnace port Any one of the methods (the same converter method) of discharging and then decarburizing and refining in the same converter is used.

  In Patent Document 2, when performing desiliconization and dephosphorization of hot metal using a converter type hot metal pretreatment furnace, a method of spraying together with top blowing oxygen using a fine powder CaO source, and a bottom blowing tuyere It is disclosed that a method of blowing a CaO source is used in combination. Patent Document 2 does not clearly indicate whether the target method is a separate converter method or the same converter method, and only refers to dephosphorization refining, and does not refer to decarburization refining.

  In both the separate converter method and the same converter method, for the sake of convenience, the first half of refining is named “dephosphorization refining”, and the second half of refining is named “decarburization refining”. Often doing. Therefore, also in decarburization refining, finishing dephosphorization refining ability can be improved more by blowing powder with oxygen gas from a lance. On the other hand, a carrier gas is used to transport the powder in the tube in the powder blowing path. Nitrogen gas is generally used as the carrier gas. After the powder transfer path and oxygen gas flow path merge, oxygen gas, powder, and transfer gas flow in the oxygen gas flow path, and oxygen gas, powder, and transfer gas flow from the tip of the lance to the surface of the melt. Is sprayed on. When nitrogen gas is used as the carrier gas, the nitrogen gas is once dissolved in the molten metal, causing a rise in the nitrogen concentration of the molten metal. When the target component of the molten steel to be melted is low nitrogen steel, it is not preferable that the nitrogen concentration in the blown molten steel increases due to the carrier gas. On the other hand, in the converter refining method by the same converter method using the converter having the powder blowing lance device of the present invention, powder is blown together with oxygen gas from the lance at the initial stage of decarburization refining, In the final stage, it is preferable to blow only oxygen gas without blowing powder from the lance. The final dephosphorization reaction is promoted by blowing powder together with oxygen gas from the lance at the beginning of decarburization refining, while at the end of decarburization refining, only oxygen gas is blown without blowing powder from the lance. Although the nitrogen concentration in the molten metal is increased by blowing the carrier gas, the nitrogen concentration of the molten metal is advanced by blowing only oxygen gas thereafter, and the nitrogen concentration in the blown molten steel can be reduced. The initial stage of decarburization refining is not particularly limited, but examples include the time period up to about 25% of the initial decarburization refining time, while the last stage of decarburization refining means the remaining time period. . Since the powder blowing lance device of the present invention is provided with a terminal valve, the terminal valve is closed at the end of decarburization refining without powder blowing to prevent high-pressure oxygen gas from filling the flexible hose for powder. it can.

  Further, in the present invention having a pressure relief valve between the upstream shut-off valve and the end valve, even if a leak occurs in the upstream shut-off valve or the end valve, in the final stage of decarburization refining in which only oxygen gas is blown from the lance to the molten metal. The leaked gas is discharged out of the system via the pressure relief valve. Therefore, even if oxygen gas leaks to the powder flexible hose side, the leaked oxygen gas does not enter the powder blowing device. Conversely, even if the nitrogen gas on the powder blowing device side leaks, since the pressure of oxygen gas is higher, it will not be mixed into the oxygen gas via the end valve. The rise can be prevented.

  In one converter factory, various varieties are usually manufactured. When dephosphorization and decarburization are separately performed in a converter, there may be a mix of varieties that perform powder blowing and non-implement varieties in dephosphorization and refining, both in the same converter method and in different converter methods. is there. Even in such a case, if the converter is equipped with the powder blowing lance device of the present invention, for the types that do not require powder blowing, only oxygen gas blowing is performed without powder blowing during dephosphorization refining. It can be carried out. Since the powder blowing lance device of the present invention is equipped with a terminal valve, in the dephosphorization refining of the type that does not perform powder blowing, the terminal valve is closed and the powdered flexible hose is filled with high-pressure oxygen gas. Can be prevented.

  When powder is blown together with oxygen gas in an upper blowing lance, as described in Patent Document 3, wear and abrasion of the nozzle at the tip of the lance may occur. On the other hand, as in the present invention, of the total refining time in the converter, for example, at the end of decarburization refining in the same converter method, only oxygen gas is blown without blowing powder from the lance, or various If only one of the varieties is blown with powder, and other varieties are blown with oxygen gas without blowing powder from the lance, the entire time of blowing oxygen gas from the lance to the surface of the molten metal Among them, the time ratio for using the powder blowing together becomes low. In such an operation mode, it is possible to prevent the lance life from being further shortened due to wear and tear of the lance due to powder blowing within the lance life time when only oxygen gas blowing is performed. Therefore, as described in Patent Document 3, the powder can be blown into the molten metal after the powder is joined to the oxygen gas without using a quadruple tube lance.

  The present invention shown in FIGS. 1 to 3 was applied to an upper bottom blowing converter with a molten steel amount of 300 tons. The converter is charged with hot metal, first dephosphorized, and after dephosphorizing, the converter is tilted while leaving the molten iron in the converter, and only the slag is discharged from the furnace port. A decarburization refining method (same converter method) is applied.

  The powder sprayed together with the oxygen gas from the tip of the upper spray lance is supplied from the powder supply device 19. In the powder supply device 19, the powder is stored in the blowing tank 20, conveyed by the carrier gas via the feeder 21 below the blowing tank, and moves in the piping of the powder conveying path 32. Nitrogen gas is used as the carrier gas. The powder conveyance path 32 is sent to the lifting platform 6 via the powder flexible hose 15, and passes through the powder flow path separating unit 16 for exchanging lances on the lifting platform, and the powder conveyance path 32 is a joining section. In 17, it merges with the U-shaped oxygen gas flow path (U-shaped portion 13). A terminal valve 7 is provided on the upstream side of the powder flow path disconnecting portion 16 on the lifting platform. The powder conveyance path 32 enters the oxygen gas flow path 31 with an inclination angle θ of 45 degrees with respect to the vertical, and in the U-shaped oxygen gas flow path, the oxygen gas flow path and the powder conveyance path are in the form of a double tube. have. An upstream cutoff valve 18 is provided in the middle of the powder conveyance path 32 and upstream of the powder flexible hose 15, and a pressure relief valve 9 is provided between the upstream cutoff valve 8 and the end valve 7.

30% of the varieties refined in this converter were blown with powder from the top lance, and the remaining varieties were not blown with powder. Also, in varieties that perform powder injection, powder removal is performed during the entire refining time in dephosphorization refining, and powder injection is performed in the initial 25% of the total decarburization refining time, and the remaining 75% of time. Then, powder blowing was not performed. As the powder, CaO powder was blown, the powder blowing speed was about 800 kg / min, and the amount of powder blown per charge was about 1 to 3 tons / charge. The carrier gas (nitrogen gas) flow rate when the powder was blown was about 2000 Nm ³ / h.

In dephosphorization refining, the acid feed rate from the top blowing lance nozzle is set to 20000 to 30000 Nm ³ / h to suppress the stirring of the molten steel by the top blowing oxygen jet and the nozzle back pressure when only oxygen is blown. Was about 0.25 to 0.35 MPa. In the decarburization refining, in order to promote decarburization refining by stirring the molten steel with an upper blowing oxygen jet, the acid feed rate from the upper blowing lance nozzle is set to 60000-70000 Nm ³ / h, and when only oxygen is blown, the nozzle back pressure is 0. The pressure was about 65 to 0.75 MPa. When powder was blown from the top blowing lance and the powder blowing speed was about 800 kg / min, the nozzle back pressure of the top blowing lance increased by about 0.2 MPa compared to the case where no powder was blown.

  The nozzle back pressure becomes the highest when powder blowing is used in combination with decarburization refining. Even at this time, the nozzle back pressure could be less than 1 MPa.

  In refining the converter, when only oxygen gas is blown without blowing powder from the tip of the lance, the end valve 7 and the upstream shut-off valve 18 are closed and the pressure relief valve 9 is released, and oxygen gas is fed together with powder from the tip of the lance. At the time of blowing, the end valve 7 and the upstream shut-off valve 18 were opened and the pressure relief valve 9 was closed.

  Converter refining was performed under the above conditions. As a result, the life of the lance was about 300 charges, and there was no change from when no powder was blown. As a result of observing the nozzle of the lance that had reached the end of its life, no particular wear of the nozzle due to powder blowing was observed. In addition, damage to the flexible hose for powder was not particularly observed. Therefore, it was confirmed that the specification (general specification) that does not need to consider the influence of the back pressure of oxygen can be used as the flexible hose for powder.

DESCRIPTION OF SYMBOLS 1 Converter 2 Top blowing lance 3 Nozzle 4 Lifting device 5 Lifting guide device 6 Lifting stand 7 Terminal valve 8 Inner tube 9 Pressure relief valve 11 Oxygen flexible hose 12 Oxygen flow path separation part 13 U-shaped part 14 Lance upper end 15 Powder Body flexible hose 16 Powder flow path disconnecting section 17 Merge section 18 Upstream shut-off valve 19 Powder supply device 20 Blowing tank 21 Feeder 22 Fitting 31 Oxygen gas flow path 32 Powder transport path θ Inclination angle

Claims (6)

A powder blowing lance device for spraying powder together with oxygen gas to the molten metal in the converter, the lance lifting device for raising and lowering the lance includes a lifting guide device and a lifting stand, and the lifting stand is a lifting guide device The lance is attached to the lifting platform, oxygen gas is sent to the lifting platform by an oxygen flexible hose, and the oxygen gas channel on the lifting platform is separated from the oxygen channel for lance replacement. Through the section, bent into a U-shape and fed into the lance from the upper end of the lance,
The powder is sent to the lifting platform together with the carrier gas by the flexible hose for powder, and the powder transportation path is a U-shaped oxygen gas channel through the powder channel separation part for lance replacement on the lifting platform . After joining the curved pipe , the powder is blown along with oxygen gas to the molten metal in the converter via all nozzles at the bottom of the lance,
A powder blowing lance device comprising a shut-off valve (hereinafter referred to as “end valve”) in the middle of a powder conveyance path on a lifting platform and upstream of the separation portion. At a position where the powder transport path from entering the curved pipe portion of the U-shaped oxygen gas channel, the powder transport path enters the oxygen gas flow path with an inclination angle to the vertical, U-shaped oxygen gas stream In at least a part of the curved pipe portion of the path, the oxygen gas flow path and the powder conveyance path have a double pipe shape, and the powder directly enters the vertical lance from the end of the inner pipe of the double pipe. 2. The powder blowing lance device according to claim 1 , wherein an inner tube is arranged so as to be introduced. The upstream shut-off valve is provided in the middle of the powder conveyance path and upstream of the powder flexible hose, and a pressure release valve is provided between the upstream shut-off valve and the end valve. Or the powder blowing lance apparatus of Claim 2. A powder blowing method using the powder blowing lance device according to claim 1 or 2, wherein at the time of blowing only oxygen gas without blowing powder from the tip of the lance, the end valve is closed and A powder blowing method, wherein the end valve is opened when oxygen gas is blown together with the powder.   4. A powder blowing method using the powder blowing lance device according to claim 3, wherein at the time of blowing only oxygen gas without blowing powder from the tip of the lance, the terminal valve and the upstream shut-off valve are closed and a pressure relief valve. The powder blowing method is characterized by opening the terminal valve and the upstream shut-off valve and closing the pressure release valve when oxygen gas is blown together with powder from the tip of the lance. A converter refining method using a converter having a powder blowing lance according to any one of claims 1 to 3, carried out first dephosphorization refining the molten iron was charged into a converter, The molten slag is discharged from the converter furnace port while leaving the molten metal in the converter after dephosphorization and refining, and then when decarburizing and refining, powder is blown together with oxygen gas from the lance during the dephosphorization and refining, A converter refining method, wherein powder is blown together with oxygen gas from the lance at an early stage of decarburization refining, and oxygen gas is blown without blowing powder from the lance at the end of decarburization refining.

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