JP5644355B2 - Hot metal refining method - Google Patents

Description

  The present invention relates to a refining top blowing lance suitable for subjecting hot metal or molten steel in a converter-type refining vessel to oxidative refining such as dephosphorization, and more specifically, a supply path for oxygen-containing gas and a solid such as iron oxide. Oxygen-containing gas and solid oxygen source can be independently supplied from these paths to the hot metal or molten steel bath surface in the converter-type smelting vessel, and the oxygen-containing gas In addition, powder other than the solid oxygen source can be supplied, and oxygen-containing gas for secondary combustion can be supplied from the side surface of the lance separated from the tip of the lance to the in-furnace space of the converter-type refining vessel. The present invention relates to a possible refining top lance and a method for refining hot metal using this refining top lance.

  In the steelmaking process using blast furnace hot metal, before decarburizing and blowing in the converter, most of the phosphorus (P) contained in the hot metal is oxidized and removed using oxygen gas or solid iron oxide. The preliminary dephosphorization process is generally performed. In particular, in recent years, quality requirements for steel products have become more stringent than ever, and there has been a demand for a lower phosphorus concentration than ever before. In order to meet this quality requirement, it is necessary to increase the amount of hot metal to be subjected to dephosphorization more than before, or to stably reduce the phosphorus concentration after dephosphorization.

On the other hand, reduction of slag emissions in the steelmaking process is indispensable in order to respond to demands for reducing the environmental impact represented by recent global warming. To reduce the amount of slag discharged by the preliminary dephosphorization of hot metal, slag that melts and functions as a refining agent for absorbing phosphorus oxide (P ₂ O ₅ ) (referred to as “slag for dephosphorization refining”) It is necessary to reduce the amount of dephosphorization refining agent (hereinafter referred to as “dephosphorization refining agent”). The main dephosphorizing refining agent in hot metal preliminary dephosphorization treatment is lime.To meet the above quality requirements and reduce slag discharge, the amount of dephosphorization is reduced while reducing the amount of lime used. The technology to maintain, that is, the technology to efficiently dephosphorize with a small amount of lime is required.

  In the hot metal preliminary dephosphorization process, lime that does not hatch (slag) does not contribute to the dephosphorization reaction, so in order to reduce the amount of lime used, it is important to promote the hatching of the added lime. Become. Conventionally, fluorite (ore containing calcium fluoride as a main component) is known as a medium solvent for promoting hatching, which is excellent in hatching ability of slag including lime, and fluorite is also used in dephosphorization treatment. Has been used. However, in recent years, with the tightening of environmental regulations, the use of a solvent containing fluorine has been restricted, and therefore, means for promoting the dephosphorization reaction by lime have been studied without using fluorite. Proposals have been made.

  As one of the means, a lime-based dephosphorizing refining agent is supplied to the same location or a location where an oxygen source such as an oxygen-containing gas or iron oxide is supplied, and the lime-based dephosphorization agent is used. A technique has been proposed in which hatching of a refining agent is promoted and dephosphorization treatment is efficiently performed with a small amount of a refining agent for dephosphorizing lime.

  For example, Patent Document 1 proposes a hot metal preliminary dephosphorization treatment method in which a lime-based dephosphorization refining agent and an endothermic substance are added to a place where oxygen gas is supplied. In Patent Document 2, as a top blowing lance suitable for adding a lime-based dephosphorization refining agent to a hot spot region formed on the hot metal surface by supplying oxygen gas, a lime-based dephosphorization refining is provided at the axial center position. An upper blowing lance having a quadruple tube structure is disclosed in which a powder blowing nozzle for supplying an agent is arranged and a plurality of nozzles for supplying oxygen gas are arranged around the nozzle. Further, in Patent Document 3, a supply path for supplying a lime-based dephosphorization refining agent together with an oxygen-containing gas and an iron oxide supply path are separated, and oxygen-containing gas and lime-based dephosphorization are separated from these paths. An upper blowing lance for refining a five-pipe structure for supplying a refining agent and iron oxide to the hot metal bath surface and subjecting the hot metal to oxidative refining such as dephosphorization has been proposed. This patent document 3 also proposes detecting a broken hole in the iron oxide supply path by providing a buffer space around the iron oxide supply path.

  By the way, since the dephosphorization reaction in molten iron is more advantageous as the temperature is lower, the dephosphorization treatment is performed at a hot metal stage of about 1300 to 1400 ° C. For example, Patent Literature 1 and Patent Literature 2 disclose preliminary dephosphorization treatment of hot metal at about 1300 ° C. to about 1350 ° C. In addition, recently, since the free board is large and strong stirring is possible, the preliminary dephosphorization treatment of the hot metal is generally performed in a converter type refining vessel. However, because of the low temperature, the hot metal scattered during the dephosphorization process adheres to and solidifies on the side walls and furnace opening of the converter-type smelting vessel and deposits the metal, resulting in a reduction in the hot metal yield and the production of the metal. It was causing a decline in sex.

  The problem of metal adhesion is not limited to the hot metal preliminary dephosphorization process, but is also a problem in hot metal decarburization refining in a converter. In other words, in the decarburization and refining of hot metal in the converter, the metal is blown to the inner wall and the furnace port of the converter due to the scattering of the metal during blowing (referred to as “spitting”) and the slag ejection (referred to as “slipping”). There are problems such as accumulation, hot metal in the furnace, and charging of iron scrap are hindered.

  Many means for solving the adhesion of the metal have been proposed. For example, in Patent Document 4, a horizontal or downward secondary combustion nozzle is disposed on a side surface of an upper blowing lance that is spaced a predetermined distance from a distal end portion of an upper blowing lance having a main hole nozzle at the distal end portion. A refining method is proposed in which oxygen gas is supplied from the main hole nozzle to oxidize and refine hot metal or molten steel in the converter, and at the same time, oxygen gas is supplied from the secondary combustion nozzle to melt the metal attached to the converter. Has been.

JP 2003-328021 A JP 2006-336033 A JP 2008-208407 A JP 2008-138271 A

  Currently, in the steelmaking process, starting with hot metal dephosphorization, a gaseous oxygen source such as an oxygen-containing gas and a solid oxygen source such as iron oxide are used together as an oxygen source, and these are located at the same location or in close proximity. The oxidation refining method added to the mainstream has become the mainstream. In that case, the flux is added to the gaseous oxygen source by using the gaseous oxygen source as a carrier gas and carrying a flux such as a dephosphorizing refining agent together with the gaseous oxygen source (see Patent Document 3). The refining method to put in the position is also performed. Also, even when such refining is carried out, it is possible to dissolve the metal adhering to the inner wall and furnace port of the converter type refining vessel by the gaseous oxygen source supplied from the secondary combustion nozzle on the side of the top blowing lance. It is extremely important in securing iron yield and productivity.

  If the conventional various types of top blowing lances are verified as the top blowing lances for carrying out such refining, any top blowing lances cannot be employed. Moreover, even if the conventional top blowing lance is combined, it cannot be a satisfactory top blowing lance. For example, even if the secondary combustion nozzle proposed in Patent Document 4 is installed by connecting to the oxygen-containing gas supply path of the top blowing lance proposed in Patent Document 3, oxygen is supplied through the oxygen-containing gas supply path. When the flux is transported together with the contained gas, there arises a problem that the secondary combustion nozzle is blocked by the flux.

  The present invention has been made in view of such circumstances, and the object thereof is to efficiently perform hot metal or hot steel in an oxidizing refining vessel in a converter-type refining vessel, such as preliminary dephosphorization of hot metal. It is possible to provide an upper blowing lance for refining that can efficiently dissolve the metal that has adhered to the converter-type refining vessel, and at the same time, which enables efficient oxidation refining. It is to provide a method for refining the hot metal used.

The gist of the present invention for solving the above problems is as follows.
(1) A refining top blow lance used for the oxidation refining of hot metal or molten steel contained in a converter-type refining vessel, and a main hole for refining vertically or obliquely downward at the tip of the top blow lance A nozzle and a sub-hole nozzle for blowing a solid oxygen source, a secondary combustion nozzle in a horizontal or obliquely downward direction on the side surface of the upper blowing lance at a position separated upward from the tip, and an upper In the blowing lance, powder different from the solid oxygen source is supplied through the main hole nozzle together with the oxygen-containing gas for blowing, or oxygen-containing gas for blowing is supplied through the main hole nozzle. A second supply path for supplying an oxygen-containing gas for secondary combustion through the secondary combustion nozzle, a powdered solid oxygen source, and a carrier gas. And through the sub-hole nozzle And a third supply passage for supplying the same, a refining top blow lance.
That is, the first supply path includes a refining flux introduction section that introduces a powder (hereinafter also referred to as “refining flux”) different from the solid oxygen source, and an oxygen that introduces an oxygen-containing gas into the path. And a contained gas introduction part. The refining flux introduction part may be an introduction part that introduces the refining flux together with the carrier gas, and the carrier gas is also preferably an oxygen-containing gas. Needless to say, a structure in which the refining flux and the oxygen-containing gas are introduced from the same introduction portion (that is, a mixture in which the refining flux and the oxygen-containing gas are mixed in advance at a ratio when the refining flux and the oxygen-containing gas are supplied through the main hole nozzle. Or a structure introduced from the introduction portion). In operation, the introduction of the refining flux may be stopped, and only the oxygen-containing gas may be introduced from the oxygen-containing gas introduction section into the first supply path.
In addition, the second supply path has an oxygen-containing gas introduction unit that introduces the oxygen-containing gas into the path. Furthermore, the third supply path has a solid oxygen source introduction unit that introduces a solid oxygen source into the path together with the carrier gas. In operation, the supply of the solid oxygen source may be stopped, and only the carrier gas may be introduced into the third supply path from the solid oxygen source introduction unit. Here, the first supply path and the second supply path may share the oxygen-containing gas introduction unit. In that case, a partition structure is provided to prevent the refining flux from entering the second supply path.
(2) The end of the second supply path is closed, and the oxygen-containing gas supplied through the second supply path is configured not to join the first supply path and the third supply path. The top blowing lance for refining as described in said (1) characterized by the above-mentioned. Here, the end of the second supply path means a portion of the path ahead of the nozzle for secondary combustion closest to the lance tip (on the lance tip).
(3) It is configured to supply any one kind or two kinds or more of reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas to the second supply path. The top blowing lance for refining according to (2) above. In other words, the second supply path has an introduction section for introducing any one or more of the above gases into the path. Needless to say, a structure may be adopted in which these gases are introduced from the same introduction portion as the oxygen-containing gas.
(4) A buffer space in which any one or more of air, reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas is present is provided around the third supply path. The above (1) to (3) are characterized in that a broken hole in the third supply path is detected based on a change in pressure or flow rate of gas existing in the buffer space. An upper blowing lance for refining according to any one of the above.
(5) The said 1st supply path | route, the said 2nd supply path | route, and the said 3rd supply path | route are arrange | positioned on the concentric circle, In any one of said (1)-(4) characterized by the above-mentioned. Top blown lance for refining.
(6) Add lime-based dephosphorizing refining agent to the hot metal contained in the converter-type refining vessel, hatch the added dephosphorizing refining agent to form slag, and carry out oxidative refining for hot metal In doing so, using the top blowing lance for refining according to any one of the above (1) to (5), the oxygen gas for blowing is supplied from the first supply path to the hot metal bath surface, The solid oxygen source is supplied to the hot metal bath surface in the vicinity of the location where the oxygen gas for blowing is supplied from the supply path, and the oxygen gas for secondary combustion is converted from the second supply path. A method for refining hot metal, which comprises supplying to the furnace space of a furnace-type refining vessel and carrying out oxidation refining. In addition, it is preferable to supply at least a part of the refining agent for lime-based dephosphorization to the hot metal from the first supply path.

  According to the present invention, the top blowing lance is supplied with a powder different from the solid oxygen source, such as a lime-based dephosphorizing refining agent, together with the oxygen-containing gas for blowing through the main hole nozzle. Alternatively, a first supply path for supplying the oxygen-containing gas for blowing through the main hole nozzle, and a second supply path for supplying the oxygen-containing gas for secondary combustion through the nozzle for secondary combustion And a third supply path for supplying the powdered solid oxygen source together with the carrier gas through the sub-hole nozzle, so that the powder is supplied from the first supply path and the third supply path. Even if supplied, only the oxygen-containing gas is injected from the secondary combustion nozzle, and the secondary combustion nozzle stably injects the oxygen-containing gas for secondary combustion over a long period of time without clogging. Thereby, the adhesion of the metal in the converter-type smelting vessel is suppressed, the adverse effects associated with the adhesion of the metal are prevented, and an improvement in iron yield and productivity are achieved. In addition, fluxes such as oxygen-containing gas, solid oxygen source, and lime-based dephosphorizing refining agent can be supplied to the same location or in the vicinity of each, enabling efficient smelting of hot metal and molten steel. Is done.

It is a schematic sectional drawing which shows the example of the upper blowing lance for refining which concerns on this invention. It is a figure which shows the supply path | route of the buffer gas to buffer space in the upper blowing lance for refining which concerns on this invention. It is a schematic sectional drawing which shows the other example of the upper blowing lance for refining which concerns on this invention.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In addition, although the top blowing run illustrated below is a typical example, the shape of each part (a nozzle, a path | route, etc.), a dimension, a number, a position, etc. are not limited to this. That is, in order to properly realize the purpose of each part, a structure can be designed according to an actual use environment with reference to a known technique.

  FIG. 1 is a schematic cross-sectional view showing an example of a refining top blow lance according to the present invention. As shown in FIG. 1, an upper blowing lance 1 according to the present invention includes a cylindrical lance main body 2, a lance nozzle 3 connected to the lower end of the lance main body 2 by welding, and the upper end of the lance main body 2. There is a lance top 4 serving as a gas, powder, and cooling water introduction part (connecting part to each supply facility of the lance body 2). The lance body 2 is composed of six outermost tubes 5, outer tubes 6, middle tubes 7, partition tubes 8, inner tubes 9, and innermost tubes 10 of six kinds of concentric steel tubes, that is, six-fold tubes, which are made of copper. The nozzle 3 is provided with a vertically downward sub-hole nozzle 12 at the axial center thereof, and around the auxiliary hole nozzle 12, a plurality of main hole nozzles 11 whose discharge direction is a vertically oblique downward direction are provided. Has been. In addition, a plurality of secondary combustion nozzles 13 whose discharge direction is horizontal or obliquely downward is provided on the side surface of the lance body 2 at a position separated upward from the tip of the lance nozzle 3. It is installed at almost equal intervals in the circumferential direction. In FIG. 1, although there are two stages in the vertical direction, there may be one stage or three stages or more. If the secondary combustion nozzle 13 in the horizontal or obliquely downward direction is provided on the side surface portion at a position separated upward from the tip of the upper blow lance 1, the injection direction from the secondary combustion nozzle 13 is such that the injection direction of the smelting vessel This means that the position and direction (angle) on the side surface of the lance are selected so as to face the furnace wall. In addition, the distance from the tip of the lance of the secondary combustion nozzle 13 closest to the tip of the lance is 300 mm or more away from the tip of the lance in consideration of design constraints such as a cooling water channel in the general lance nozzle 3. It is preferable.

  The main hole nozzle 11 is an oxygen-containing gas that is a blowing gas, or a powder ("refining flux") such as a flux other than a solid oxygen source together with the oxygen-containing gas using the oxygen-containing gas as a carrier gas, that is, It is a nozzle for blowing powder such as a lime-based dephosphorizing refining agent into a refining vessel (not shown) such as a converter, and the sub-hole nozzle 12 is a solid oxygen source such as iron ore or mill scale. The secondary combustion nozzle 13 is a nozzle for blowing an oxygen-containing gas for secondary combustion into the internal space of the smelting vessel. As shown in FIG. 1, the main hole nozzle 11 has a so-called Laval nozzle shape in which the cross section expands toward the tip. On the other hand, the sub-hole nozzle 12 and the secondary combustion nozzle 13 have a straight shape, but the sub-hole nozzle 12 and the secondary combustion nozzle 13 may also take the shape of a Laval nozzle. The upper blowing lance 1 is supported by a support device (not shown) above the refining vessel so that it can be moved up and down inside the refining vessel.

In the upper blowing lance 1 of FIG. 1, there are no particular restrictions on the number of installed holes and the diameter of the main hole nozzle 11, but due to restrictions such as the supply gas pressure to the upper blowing lance 1, the required oxygen-containing gas supply amount can be reduced. Since the number of holes to be installed and the diameter are inevitably determined, they should be set within a range that satisfies them. The secondary combustion nozzle 13 is not particularly limited in terms of the number of installed holes and the diameter, but is set to an arrangement suitable for melting the adhered metal depending on the furnace shape. Here, the oxygen-containing gas is a gas having oxygen gas (pure oxygen gas), oxygen-enriched air, a mixed gas of oxygen gas and rare gas, and the oxygen gas concentration is higher than that of air. is there. As the solid oxygen source blown from the sub-hole nozzle 12, iron ore sintered ore, mill scale, dust collection dust, iron sand, iron ore and the like can be used. Here, the dust collection dust is dust containing FeO or Fe ₂ O ₃ that is recovered from exhaust gas in a blast furnace, a converter, and a sintering process.

  In the present invention, a flux such as quick lime, which is a kind of lime-based dephosphorizing refining agent, blows oxygen-containing gas from the main hole nozzle 11 as a carrier gas. A flux such as quick lime may be blown in combination with the oxygen source. Of course, the flow rate ejected from the sub-hole nozzle 12 and the flow rate ejected from the main hole nozzle 11 are independently controlled by independent flow meters (not shown).

  The gap between the outermost pipe 5 and the outer pipe 6 and the gap between the outer pipe 6 and the middle pipe 7 serve as a cooling water flow path for cooling the top blowing lance 1, and are provided at the top of the lance 4. The cooling water supplied from the supplied water supply pipe (not shown) passes through the gap between the outer pipe 6 and the middle pipe 7 to reach the lance nozzle 3, and reverses at the lance nozzle 3 to reverse the outermost pipe 5. The water is discharged from a drain pipe (not shown) provided on the lance top 4 through a gap between the outer pipe 6 and the outer pipe 6. The water supply / drainage route may be reversed.

  The gap between the intermediate pipe 7 and the partition pipe 8 is a second supply path for supplying the oxygen-containing gas to the secondary combustion nozzle 13 and communicates with the intermediate pipe 7 provided at the lance top 4. The oxygen-containing gas introduced from the oxygen-containing gas supply pipe 14 into the middle pipe 7 reaches the secondary combustion nozzle 13 through the second supply path, and is ejected from the secondary combustion nozzle 13. It has become. However, since the upper end portion of the partition pipe 8 does not reach the installation site of the oxygen-containing gas supply pipe 14 (the introduction part of the oxygen-containing gas), it was introduced from the oxygen-containing gas supply pipe 14 into the middle pipe 7. The oxygen-containing gas also flows into the gap between the partition pipe 8 and the inner pipe 9 (as described later, the gap between the partition pipe 8 and the inner pipe 9 is the first supply path), and passes through this gap. It ejects to the main hole nozzle 11. Further, since the lower end portion of the partition tube 8 does not reach the portion of the lance nozzle 3, it passes through the gap between the intermediate tube 7 and the partition tube 8, that is, through the second supply path, but from the secondary combustion nozzle 13. The oxygen-containing gas that has not been ejected joins the first supply path and is ejected from the main hole nozzle 11.

  The gap between the partition pipe 8 and the inner pipe 9 is an oxygen-containing gas for blowing or a powder different from the oxygen-containing gas and a solid oxygen source (“refining flux”), for example, smelting for lime-based dephosphorization This is a first supply path for supplying powder such as an agent to the main hole nozzle 11. In other words, the lance top 4 is provided with a powder supply pipe 15 for supplying a refining flux using oxygen-containing gas as a carrier gas (a portion where the supply pipe is installed serves as a refining flux introduction part). The oxygen-containing gas supply pipe 14 is provided in communication with the middle pipe 7 as described above. When the refining flux is blown together with the blowing oxygen-containing gas from the main hole nozzle 11, the oxygen-containing gas supplied from the oxygen-containing gas supply pipe 14, the powder supplied from the powder supply pipe 15, and the oxygen-containing gas The gas merges and passes through the first supply path. In this case, since the lower end position of the partition pipe 8 is below the installation position of the secondary combustion nozzle 13, the powder passing through the first supply path does not flow into the secondary combustion nozzle 13. That is, the partition pipe 8 functions as a partition structure for preventing the refining flux from being mixed into the second supply path. When only the oxygen-containing gas for blowing is blown from the main hole nozzle 11, the powder supply pipe 15 may be stopped or only the oxygen-containing gas may be supplied from the powder supply pipe 15.

As the refining flux, that is, the powder different from the solid oxygen source, all known (or foreseeable) solid substances introduced to efficiently refining other than the solid oxygen source can be applied. For example, in addition to the lime-based dephosphorizing refining agent (quick lime (CaO), limestone (CaCO ₃ ), dolomite (CaCO ₃ .MgCO ₃ ), decarburized slag, secondary refining slag, etc.), raw materials for slag ( Examples thereof include silica (SiO ₂ ), brick scraps containing magnesium oxide, etc., hatching accelerators (including fluorite, titanium oxide, aluminum oxide, etc.) and the like. Normally, at least a lime-based dephosphorizing refining agent is supplied as a refining flux.

  The inside of the innermost pipe 10 is a third supply path for supplying a solid oxygen source to the sub-hole nozzle 12 together with the carrier gas, and communicates with the innermost pipe 10 provided at the lance top 4. The solid oxygen source supplied into the innermost pipe 10 together with the transfer gas from a supply pipe (not shown) passes through the innermost pipe 10 to the subhole nozzle 12 and is ejected from the subhole nozzle 12. It has become so. Here, the installation section (not shown) of the supplier is a solid oxygen source introduction section. As the transport gas for transporting the solid oxygen source, a gas having an oxygen content equal to or lower than air is preferable, and any one of air, reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas or Two or more gases are used.

  The reason for using air, reducing gas, carbon dioxide gas, non-oxidizing gas, or noble gas as the carrier gas for the solid oxygen source is as follows. The air contains less oxygen gas than the oxygen-containing gas blown from the main hole nozzle 11, and the reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas substantially contain oxygen gas. Not in. Accordingly, combustion during transportation of a small amount of metallic iron contained in the solid oxygen source can be prevented, and combustion of the innermost tube 10 by a spark generated by contact between the solid oxygen source and the innermost tube 10 during transportation. Can be prevented. Here, the reducing gas is a hydrocarbon gas such as propane gas and CO gas, the non-oxidizing gas is a gas having no oxidizing ability such as nitrogen gas, and the rare gas is Ar gas or He. An inert gas such as a gas.

  The gap between the inner tube 9 and the innermost tube 10 is sealed at the tip of the lance nozzle 3 and is dead end, and is provided at the top of the lance 4 and is a buffer gas supply tube communicating with the inner tube 9. This is a buffer space in which any one or more of air, reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas supplied from 16 is present. In the present invention, the gas present in the buffer space is referred to as “buffer gas”.

  A supply path of the buffer gas to the buffer space is shown in FIG. As shown in FIG. 2, a buffer gas introduction device provided with a detector 20, a remote control valve 21, a flexible hose 22, and a plurality of manual shut-off valves 23 in a buffer gas supply pipe 16 provided at the lance top 4. 19 is connected, and the buffer gas is supplied to the buffer space via the buffer gas introducing device 19. As the detector 20, a pressure gauge or a flow meter, or both a pressure gauge and a flow meter are installed. As a method of introducing the buffer gas into the buffer space, the remote control valve 21 may be shut off and the buffer gas may be sealed in the buffer space, or the remote control valve 21 may be opened to buffer the buffer space. The gas pressure may always be applied. In the example of FIG. 2, both operations are possible. In addition, the flexible hose 22 is a margin when the upper blowing lance 1 moves up and down. In the example of FIG. 2, the detector 20 is installed closer to the upper blowing lance 1 than the flexible hose 22. However, the detector 20 may be installed closer to the supply side than the flexible hose 22. You may install in the part. However, when a broken hole is detected based on a measured value of pressure fluctuation in the buffer space, the detector 20 needs to be arranged on the upper blowing lance 1 side than the remote control valve 21. Therefore, from the viewpoint of operational flexibility, the detector 20 is preferably disposed on the upper blowing lance 1 side than the remote control valve 21.

  The reason for using air, reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas as the buffer gas is the same as the reason for using these gas species as the carrier gas for the solid oxygen source. In other words, even if the buffer gas and the solid oxygen source come into contact with each other even if a hole is generated in the innermost tube 10 which is the supply path of the solid oxygen source, that is, the third supply path, due to the transport of the solid oxygen source As long as this gas species is used as a buffer gas, combustion of metallic iron in the solid oxygen source and combustion of the innermost tube 10 due to sparks generated by contact between the solid oxygen source and the innermost tube 10 can be prevented. Because it can. Therefore, any gas other than the above can be used as a buffer gas as long as the gas has an oxygen content equal to or lower than air.

  A broken hole during refining of the innermost pipe 10 can be detected as follows. That is, when a hole breaks in the innermost pipe 10 during refining, the buffer space communicates with the inside of the innermost pipe 10, and the pressure in the buffer space changes or the flow rate of the buffer gas supplied to the buffer space is increased. Since it changes, a hole is detected based on the change. As specific detection methods, the following two methods can be employed. One method is to install a pressure gauge or both a pressure gauge and a flow meter as the detector 20, introduce a buffer gas into the buffer space, shut off the remote control valve 21, and buffer the gas into the buffer space. And the pressure in the buffer space is measured by the detector 20 during refining to detect a broken hole. In another method, a flow meter is installed as the detector 20, the remote control valve 21 is opened, and the pressure of the buffer gas is constantly applied to the buffer space. In this state, the flow rate is measured by the detector 20, and the hole is broken. This is a method for detecting a broken hole from a change in flow rate.

  Hereinafter, an example in which the hot metal preliminary dephosphorization process is performed in the converter using the upper blow lance 1 according to the present invention configured as described above will be described.

The upper blow lance 1 according to the present invention is disposed at a predetermined position above the hot metal in the converter, and oxygen gas is blown from the main hole nozzle 11 toward the hot metal bath surface as an oxygen-containing gas, and air is supplied from the sub hole nozzle 12 to the air. Then, a solid oxygen source is sprayed toward the hot metal bath surface using any one or more of reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas as a carrier gas. The solid oxygen source sprayed from the sub-hole nozzle 12 is supplied to or near the hot metal bath surface where the oxygen gas is supplied. The dephosphorization treatment requires a slag for dephosphorization and refining to absorb the phosphorus oxide (P ₂ O ₅ ) produced by the dephosphorization reaction. Add agent.

The refining agent for lime-based dephosphorization is not particularly limited as long as it contains CaO and can be dephosphorized as intended in the present case. Usually, it consists of CaO alone, or contains 50 mass% or more of CaO, and contains other components as necessary. As specific examples, quick lime (CaO), limestone (CaCO ₃ ), or dolomite (CaCO ₃ .MgCO ₃ ) can be used. Further, as a hatching accelerator for these substances, titanium oxide, What mixed the substance containing aluminum oxide and magnesium oxide can also be used. In addition, decarburization slag, ladle slag, and the like are mainly composed of CaO and have a low phosphorus content, so that they can be sufficiently used as a refining agent for lime-based dephosphorization.

  On the hot metal bath surface, the location where the oxygen gas collides with the hot metal bath surface (referred to as “fire point”) is heated due to the reaction between the oxygen gas and carbon in the hot metal, and is supplied to the fire point or near the fire point. The resulting solid oxygen source melts rapidly and increases the FeO component in the slag. As a result, the oxygen potential of the slag rises, that is, the slag optimum for the dephosphorization reaction is rapidly formed, and the dephosphorization process can be performed even at a small amount of slag or at a high temperature. Also, by introducing a lime-based dephosphorization refining agent at or near the fire point, hatching of the lime-based dephosphorization refining agent is promoted, and dephosphorization refining slag is formed at an early stage. The reaction is further promoted. Therefore, it is preferable to introduce the lime-based dephosphorizing refining agent to the fire point or the vicinity of the fire point through the main hole nozzle 11 or the main hole nozzle 11 and the sub hole nozzle 12.

  At the time of this blowing, oxygen gas for secondary combustion is supplied from the secondary combustion nozzle 13, and the ingot in the furnace body is melted in parallel with the dephosphorization or the ingot is prevented from adhering. As a result, adverse effects associated with the adhesion of bullion are prevented in advance, and iron yield and productivity can be improved.

In this case, the supply amount (Q) of oxygen gas from the secondary combustion nozzle 13 is preferably in the range of 5 to 30% of the supply amount (Q _O ) of oxygen gas from the main hole nozzle 11. If Q × 100 / Q 2 _O is less than 5%, the amount of oxygen gas for secondary combustion is too small, and the calorific value of secondary combustion is insufficient, so that the adhered metal cannot be dissolved. On the other hand, when Q × 100 / Q 2 _O exceeds 30%, the secondary combustion exothermic heat becomes excessive, and the melting loss of the furnace refractory is promoted.

  In addition, when the flow rate of the oxygen gas from the secondary combustion nozzle 13 becomes too fast and the oxygen gas from the secondary combustion nozzle 13 directly reaches the furnace wall, not only the adhered metal melts locally, The furnace body refractory melts locally. Therefore, during the period until the oxygen gas jet from the secondary combustion nozzle 13 reaches the furnace wall, the oxygen gas jet reacts with the CO gas generated in the furnace, and the secondary combustion heat is uniformly dispersed in the furnace. It is important to let

  As disclosed in Patent Document 4, when the flow velocity of oxygen gas from the secondary combustion nozzle 13 is attenuated to 30 m / second, the CO gas generated in the furnace and the oxygen gas from the secondary combustion nozzle 13 are reduced. It is known to react and a secondary combustion reaction occurs. The distance X (m) from the nozzle outlet of the secondary combustion nozzle 13 at which the flow rate of the oxygen gas supplied from the secondary combustion nozzle 13 is 30 m / sec is given by the following equation (1).

However, in the formula (1), V _O : the flow velocity (m / sec) of the oxygen gas jet at the outlet of the secondary combustion nozzle, de: the outlet diameter (mm) of the secondary combustion nozzle, C = 0.016 + 0.19 / (P _O −P _e ), P _O : Oxygen back pressure (kgf / cm ² ) of absolute pressure display of the secondary combustion nozzle, P _e : Atmospheric pressure (kgf) of absolute pressure display in the converter-type refining vessel / Cm ² ).

  By designing the top blowing lance and controlling the blowing conditions within an appropriate range so that this distance X does not reach the furnace wall, local melting of the metal and melting of the furnace wall refractory can be avoided. The heat of combustion reaction can be uniformly distributed in the furnace.

  In the upper blow lance 1 shown in FIG. 1, the lower end portion of the partition pipe 8 does not reach the lance nozzle 3, and the second supply path is open to the first supply path. Therefore, the flow rate of the oxygen-containing gas ejected from the secondary combustion nozzle 13 depends on the ratio of the total cross-sectional area of the main hole nozzle 11 and the total cross-sectional area of the secondary combustion nozzle 13, and the secondary combustion nozzle The amount of ejection from 13 cannot be controlled independently. That is, the total amount of oxygen-containing gas supplied from the oxygen-containing gas supply pipe 14 and the powder supply pipe 15 is distributed according to the ratio of the total cross-sectional area of both. In order to improve this and perform more accurate blowing control, the oxygen-containing gas flow rate for secondary combustion can be controlled independently. However, in this case, it is necessary to change the internal structure of the upper blowing lance from the upper blowing lance 1 shown in FIG.

  FIG. 3 shows an example of an upper blowing lance that can control the flow rate of the oxygen-containing gas for secondary combustion independently of the oxygen-containing gas for blowing.

  In the upper blow lance 1A shown in FIG. 3, the lower end of the partition tube 8 reaches the portion of the lance nozzle 3, where the gap between the middle tube 7 and the partition tube 8 is the second supply path. Sealed. Further, in the lance top portion 4, the upper end of the partition pipe 8 is located above the upper end position of the middle pipe 7, and a sealing material for sealing is installed between the middle pipe 7 and the partition pipe 8, so that the second The supply path is sealed. An oxygen-containing gas supply pipe 18 communicates with the middle pipe 7 (the supply pipe installation section serves as an oxygen-containing gas introduction section). That is, the oxygen-containing gas supplied from the oxygen-containing gas supply pipe 18 to the inside of the middle pipe 7 passes through the gap between the middle pipe 7 and the partition pipe 8, that is, the second supply path, from the secondary combustion nozzle 13. It comes to erupt.

  On the other hand, in the lance top 4, an oxygen-containing gas / powder supply pipe 17 communicates with the partition pipe 8 (the installation section of the supply pipe serves as a refining flux introduction section and an oxygen-containing gas introduction section). . In other words, the oxygen-containing gas for blowing supplied from the oxygen-containing gas / powder supply pipe 17 to the inside of the partition pipe 8 or the refining flux using the oxygen-containing gas as a carrier gas is separated from the partition pipe 8 and the inside. The gas is ejected from the main hole nozzle 11 through the gap with the pipe 9, that is, through the first supply path. When only the oxygen-containing gas is blown from the main hole nozzle 11, only the oxygen-containing gas is supplied from the oxygen-containing gas / powder supply pipe 17, and the powder is blown from the main hole nozzle 11 using the oxygen-containing gas as a carrier gas. In this case, powder is supplied together with the oxygen-containing gas from the oxygen-containing gas / powder supply pipe 17. The other structure of the top blowing lance 1A is the same as that of the top blowing lance 1 shown in FIG. 1, and the same parts are denoted by the same reference numerals, and the description thereof is omitted. Further, the preliminary dephosphorization treatment of the hot metal using the upper blowing lance 1A may be performed in accordance with the case where the upper blowing lance 1 is used.

  Depending on the state of blowing, it may not be necessary to eject oxygen gas from the secondary combustion nozzle 13 through the second supply path. In this case, in the upper blow lance 1A shown in FIG. 3, in order to prevent the secondary combustion nozzle 13 from being blocked, a reducing gas, carbon dioxide gas, non-oxidizing gas, rare gas is supplied from the second supply path. Any 1 type or 2 types or more of gas is comprised so that it can supply.

  As described above, according to the present invention, the top blowing lances 1 and 1A mainly contain powder different from the solid oxygen source, such as a lime-based dephosphorizing refining agent, together with the oxygen-containing gas for blowing. The first supply path for supplying the oxygen-containing gas for blowing through the main nozzle 11 and the oxygen-containing gas for secondary combustion through the nozzle 13 for secondary combustion. Since the second supply path for supplying and the third supply path for supplying the powdered solid oxygen source together with the carrier gas through the sub-hole nozzle 12 are provided, the first supply path and the first supply path Even if the powder is supplied from the supply path 3, only the oxygen-containing gas is injected from the secondary combustion nozzle 13, and the secondary combustion nozzle 13 is not blocked, and the secondary combustion is stable over a long period of time. Oxygen containing gas is injected. Thereby, the adhesion of the bullion to the converter-type smelting vessel is suppressed, and adverse effects associated with the adhesion of the bullion are prevented.

  The hot metal discharged from the blast furnace is desiliconized in the blast furnace casting floor as necessary, and then transferred to a 300-ton converter, using the top blow lance shown in FIG. 1 for a total of four times. The hot metal was preliminarily dephosphorized (Invention Examples 1 to 4).

  There are four main hole nozzles arranged in a concentric circle on the concentric circle, and eight secondary combustion nozzles are arranged on the circumference in a uniform arrangement on the upper and lower sides. The angle θ (°) is the distance X (m) from the nozzle outlet of the secondary combustion nozzle where the flow velocity of the oxygen gas jet from the secondary combustion nozzle is 30 m / sec. I tried to meet.

  Here, X is the distance (m) from the nozzle outlet of the secondary combustion nozzle determined from the equation (1), and H is the horizontal distance (m) from the center of the top blowing lance to the converter furnace wall. The angle θ (°) is an angle formed by the center line of the secondary combustion nozzle and the upper blowing lance, and the vertical direction is set as a reference (= 0 °). Therefore, X × sin θ represents the horizontal jet arrival distance (m) from the secondary combustion nozzle.

The phosphorus concentration in the hot metal before the dephosphorization treatment was unified to 0.12% by mass, the phosphorus concentration in the hot metal after the dephosphorization treatment was set to 0.020% by mass or less, and the iron yield was set to 98% or more. The iron yield (η) is the hot metal discharged after dephosphorization with respect to the total mass (W _O + W _S ) of the mass (W _O ) of the hot metal charged in the converter and the mass (W _S ) of the iron scrap. The mass (W) is expressed as a percentage (η = 100 W / (W _O + W _S )).

  In the dephosphorization process, oxygen gas is supplied from the oxygen-containing gas supply pipe 14, and quick lime powder (average particle size of 1 mm or less) is supplied from the powder supply pipe 15 as a carrier gas, and inside the innermost pipe. From a certain third supply path, a solid oxygen source in powder form was supplied using nitrogen gas as a carrier gas. In this case, the first supply path is a supply path for oxygen gas and quicklime powder, and the second supply path is a supply path for oxygen gas.

Apart from the top blowing lance, lump quick lime was also introduced into the furnace from the hopper provided on the converter furnace (the amount of quick lime input from the top blowing lance: the amount of quick lime input from the furnace hopper = 8: 2) . However, dephosphorization was performed without using a fluorine compound such as CaF ₂ as a dephosphorizing refining agent. Further, nitrogen gas was blown from the tuyeres at the bottom of the converter furnace at a flow rate of 0.03 to 0.30 Nm ³ / min per ton of hot metal.

The flow rate of oxygen gas supplied from the main hole nozzle and the secondary combustion nozzle was 0.6 to 2.5 Nm ³ / min per 1 ton of hot metal. The basic unit of oxygen gas was 12 Nm ³ / t excluding oxygen gas necessary for desiliconization. The oxygen gas flow rate (Q) from the secondary combustion nozzle with respect to the oxygen gas flow rate (Q _O ) from the main hole nozzle, that is, Q × 100 / Q _O was 6%. As the solid oxygen source, any one of powdered iron ore (average particle size 50 μm), iron sand (average particle size 100 μm), mill scale (average particle size 500 μm), iron ore sintered ore (average particle size 100 μm) Was sprayed from the sub-hole nozzle.

  The innermost pipe and the inner pipe were monitored for the presence or absence of broken holes from the buffer gas flow rate change, but no broken holes were generated.

  In addition, as a comparative example, a secondary combustion nozzle of the upper blow lance shown in FIG. 1 is mechanically closed, and a dephosphorization process is performed in which oxygen gas for secondary combustion is not supplied to the furnace space (Comparative Example 1). did. Other dephosphorization treatment conditions in the comparative example were performed in accordance with the examples of the present invention. Table 1 shows the hot metal components and operating conditions before and after the dephosphorization treatment in the present invention example and the comparative example. The CaO basic unit and the amount of solid oxygen source used in Table 1 are amounts per 1 ton of hot metal.

  As shown in Table 1, in all the inventive examples in which the solid oxygen source was supplied in the vicinity of the oxygen gas blowing surface from the top blowing lance, the phosphorus concentration in the hot metal after dephosphorization was 0.020% by mass or less. And the iron yield was 98% or more. On the other hand, in Comparative Example 1, the phosphorus concentration in the hot metal after the dephosphorization treatment was 0.020% by mass or less, but the iron yield was less than 98%. That is, the hot metal loss in the dephosphorization treatment was 1.2% to 1.7% in the present invention example compared with 2.1% in the comparative example, which was remarkably improved.

  The hot metal discharged from the blast furnace is desiliconized in the blast furnace casting floor as necessary, and then transferred to a 300-ton converter, using the top blow lance shown in FIG. 3 twice in total. The hot metal was preliminarily dephosphorized (Invention Examples 5 to 6).

As a result of controlling the oxygen gas flow rate from the secondary combustion nozzle to be constant during the dephosphorization process, the oxygen gas flow rate (Q) from the secondary combustion nozzle relative to the oxygen gas flow rate (Q _O ) from the main hole nozzle, that is, Q × 100 / Q 2 _O was 12%. Also in this case, it was confirmed that X × sin θ was in a range satisfying the expression (2). Other dephosphorization conditions were the same as those in Example 1. Table 2 shows hot metal components and operating conditions before and after the dephosphorization treatment. The CaO basic unit and the amount of solid oxygen source used in Table 2 are amounts per ton of hot metal, and the definition of iron yield is the same as in Example 1.

  As shown in Table 2, since the oxygen gas flow rate from the secondary combustion nozzle increased as compared with Example 1, the secondary combustion heat generation amount increased, the adhesion of the metal was further suppressed, and dephosphorization was achieved. It was confirmed that the iron yield in the treatment was almost 99% (that is, the hot metal loss was almost 1%), which was higher.

  The hot metal discharged from the blast furnace is desiliconized in the blast furnace casting floor as necessary, and then transferred to a 350-ton capacity converter using the top blow lance shown in FIGS. 1 and 3. The hot metal was subjected to preliminary dephosphorization treatment (Examples 7 to 8 of the present invention).

Oxygen gas was blown from the tuyeres at the bottom of the converter furnace as a stirring gas at a flow rate of 0.3 Nm ³ / min per ton of hot metal. The tuyeres at the bottom of the furnace had a double tube structure, and oxygen gas was blown from the inner tube and propane gas was blown from the outer tube as a cooling gas according to the flow rate of oxygen gas. As a solid oxygen source, 6 kg of iron ore sintered ore (average particle size 100 μm) was used per 1 ton of hot metal, and sprayed from the sub-hole nozzle of the top blowing lance. The condition of the oxygen jet from the secondary combustion nozzle was in a range satisfying the formula (2). Other dephosphorization conditions were the same as those in Example 1.

  In addition, as a comparative example, a dephosphorization process is performed in which the secondary combustion nozzle of the upper blow lance shown in FIG. 1 is mechanically closed and oxygen gas for secondary combustion is not supplied to the furnace space (Comparative Example 2). did. Other dephosphorization treatment conditions in the comparative example were performed in accordance with the examples of the present invention.

Table 3 shows hot metal components and operating conditions before and after the dephosphorization treatment. The oxygen gas flow rate (Q) from the secondary combustion nozzle with respect to the oxygen gas flow rate (Q _O ) from the main hole nozzle during the dephosphorization treatment, that is, Q × 100 / Q _O is also shown. The CaO basic unit in Table 3 is the amount per 1 ton of hot metal, and the definition of the iron yield is the same as in Example 1.

  As shown in Table 3, even under strong stirring conditions in which oxygen gas is blown from the bottom blowing tuyere, the increase in the secondary combustion heat generation further suppresses the adhesion of the metal, and the iron yield in the dephosphorization process is further increased. It was confirmed that

  The hot metal discharged from the blast furnace is transported to a converter with a capacity of 300 tons, and in this converter, decarburization and refining of the hot metal is performed using the top blowing lance shown in FIG. 9) In hot metal decarburization refining, dephosphorization occurs in parallel by increasing the basicity of the slag in the furnace.

  In the decarburization and dephosphorization treatment, oxygen gas is supplied from the oxygen-containing gas supply pipe 18, and quick lime powder (average particle size of 1 mm or less) is supplied from the oxygen-containing gas / powder supply pipe 17 using oxygen gas as a carrier gas. From the third supply path inside the innermost tube, a solid oxygen source in powder form was supplied using Ar gas as a carrier gas.

Apart from the top blowing lance, massive quicklime was put into the furnace from a hopper provided on the converter furnace. However, decarburization and dephosphorization were performed without using a fluorine compound such as CaF ₂ as a refining agent. Further, Ar gas was blown from the tuyeres at the bottom of the converter furnace as a stirring gas at a flow rate of 0.15 Nm ³ / min per ton of hot metal.

The flow rate of oxygen gas supplied from the main hole nozzle was 3.2 Nm ³ / min per ton of hot metal. Further, from the secondary combustion nozzle, oxygen gas was supplied in the first half of the time from the start to the end of blowing and Ar gas was supplied in the second half. The oxygen gas flow rate (Q) from the secondary combustion nozzle with respect to the oxygen gas flow rate (Q _O ) from the main hole nozzle was 5%. The condition of the oxygen jet from the secondary combustion nozzle was in a range satisfying the formula (2). As the solid oxygen source, 6 kg of iron ore sintered ore (average particle size 100 μm) was used per 1 ton of hot metal, and sprayed from the sub-hole nozzle.

  Further, as a comparative example, a dephosphorization process is performed in which the secondary combustion nozzle of the upper blow lance shown in FIG. 3 is mechanically closed and oxygen gas for secondary combustion is not supplied to the furnace space (Comparative Example 3). did. The other decarburization and dephosphorization treatment conditions of the comparative example were performed according to the examples of the present invention.

Table 4 shows the hot metal components and operating conditions before and after the dephosphorization treatment in the examples of the present invention and comparative examples. The CaO basic unit in Table 4 is the amount per 1 ton of hot metal. Iron yield (η) is the molten steel discharged after decarburization refining with respect to the total mass (W _O + W _S ) of the mass of molten iron (W _O ) charged in the converter and the mass of iron scrap (W _S ) The mass (W _I ) is expressed as a percentage (η = 100 W _I / (W _O + W _S )).

  As shown in Table 4, the iron yield of Invention Example 9 was slightly superior to that of Comparative Example 3. In other words, even under high temperature treatment and less metal adhesion, the yield could be improved by partially performing secondary combustion.

DESCRIPTION OF SYMBOLS 1 Top blowing lance 1A Top blowing lance 2 Lance main body 3 Lance nozzle 4 Lance top part 5 Outermost pipe 6 Outer pipe 7 Middle pipe 8 Partition pipe 9 Inner pipe 10 Innermost pipe 11 Main hole nozzle 12 Subhole nozzle 13 For secondary combustion Nozzle 14 Oxygen-containing gas supply pipe 15 Powder supply pipe 16 Buffer gas supply pipe 17 Oxygen-containing gas / powder supply pipe 18 Oxygen-containing gas supply pipe 19 Buffer gas introduction device 20 Detector 21 Remote control valve 22 Flexible hose 23 Manual shut-off valve

Claims (5)

Adding the lime-based dephosphorizing refining agent to the hot metal contained in the converter-type refining vessel, hatching the added dephosphorizing refining agent to form slag, and in carrying out the oxidation refining for hot metal,
A lance on for refining to be used in the oxidation refining the contained molten iron in the converter type refining vessel,
A side surface portion of the upper blowing lance at a position separated from the tip portion at the tip portion of the upper blowing lance, having a vertically downward or diagonally downward blowing main hole nozzle and a solid oxygen source blowing sub-hole nozzle. The nozzle for secondary combustion in the horizontal or diagonally downward direction,
And, inside the top blowing lance, a powder different from the solid oxygen source is supplied together with the oxygen-containing gas for blowing through the main hole nozzle, or the oxygen-containing gas for blowing is supplied to the main hole. A first supply path for supplying through a nozzle, a second supply path for supplying oxygen-containing gas for secondary combustion through the nozzle for secondary combustion, and a powdered solid oxygen source, A third supply path for supplying the carrier gas together with the auxiliary hole nozzle;
Using a fine on for refining lance that having a,
At the same time as supplying the oxygen gas for blowing from the first supply path to the hot metal bath surface, the hot metal bath near the place where the oxygen gas for blowing is supplied from the third supply path to the solid oxygen source Supply to the surface together with the transfer gas, and further supply oxygen gas for secondary combustion from the second supply path to the in-furnace space of the converter-type refining vessel to perform oxidative refining,
A method for refining hot metal, which suppresses the adhesion of metal to the converter-type refining vessel to prevent harmful effects associated with metal adhesion . The upper blow lance for refining is closed at the end of the second supply path so that the oxygen-containing gas supplied through the second supply path does not join the first supply path and the third supply path. The hot metal refining method according to claim 1, wherein the hot metal is refined . The refining top blow lance is configured to supply one or more of reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas to the second supply path. The hot metal refining method according to claim 2, wherein the hot metal is refined . The refining top blow lance has one or more of air, reducing gas, carbon dioxide gas, non-oxidizing gas, and rare gas around the third supply path. A buffer space is provided, and a hole in the third supply path is detected based on a change in pressure or flow rate of a gas existing in the buffer space. The method for refining hot metal according to any one of claims 3 to 4. 5. The refining top blow lance is characterized in that the first supply path, the second supply path, and the third supply path are arranged concentrically. The hot metal refining method according to claim 1 .

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