JP6327298B2 - Hot metal refining method - Google Patents

Description

  The present invention is directed to the hot metal that is discharged from the blast furnace and accommodated in a refining vessel such as a converter, and the oxidizing gas for refining and the powdery refining agent are sprayed from the top blowing lance to the hot metal, Regarding the hot metal refining method for performing dephosphorization treatment (hereinafter, also simply referred to as “dephosphorization treatment”) as a preliminary treatment, in detail, a flame is formed by combustion of fuel gas below the tip of the upper blowing lance. Further, the present invention relates to a hot metal refining method performed while heating a powdery refining agent supplied from an upper blowing lance.

In the steel making process, reduction of CO ₂ emissions has become an important issue, and in the steel making process, attempts have been made to increase the blending ratio of cold iron sources such as iron scrap as the iron source to be used. The reason why this attempt is made is that in the manufacture of steel products, the production of hot metal in a blast furnace requires a great deal of energy to reduce and melt iron ore, whereas the cold iron source only needs heat of melting. This is because when a cold iron source is used in the steel making process, the amount of energy used for reducing heat of the iron ore can be reduced, and the amount of CO ₂ generated can be greatly reduced.

  However, in the molten steel production process using a combination of blast furnace and converter, the melting heat source of the cold iron source is the sensible heat of the hot metal and the combustion heat due to the oxidation of carbon and silicon in the hot metal, and the cold iron source can be melted. The amount is naturally limited. Therefore, various means have been proposed in order to increase the blending ratio of the cold iron source, that is, the meltable amount of the cold iron source in the steelmaking refining process.

  For example, in Patent Document 1, when dephosphorization is performed as a hot metal pretreatment, a carbon source is added to generated slag during dephosphorization, and an oxygen source is blown into the slag to burn the carbon source. A method has been proposed in which this combustion heat is applied to the hot metal.

  Patent Document 2 discloses a method in which carbonaceous materials such as coal, coke, pitch, and heavy oil are blown together with oxygen into a molten iron bath for gasification, and at the same time, iron scrap is melted and refined. A gasifying agent blowing nozzle on the outside of the nozzle, and an oxidation for secondary combustion of the product gas generated in the furnace whose nozzle central axis is inclined at an angle of 20 to 60 ° with respect to the lance axis. There has been proposed a method of melting and refining iron scrap while performing gasification of a carbonaceous substance and simultaneously performing secondary combustion of the gas generated in the furnace using an upper blowing lance having an agent blowing nozzle.

  Patent Document 3 discloses that when decarburizing hot metal in a converter, it is independent of the main hole for oxygen ejection and the supply flow path of oxygen gas ejected from the main hole, and is used for fuel gas, oxygen gas and refining. Using an upper blowing lance having a flux supply sub-hole capable of jetting flux simultaneously, the oxygen gas jets ejected from the oxygen jet main holes are kept separated from each other and independently of the oxygen gas jets There has been proposed a decarburization processing method in which a flame is formed at the tip of the flux supply sub-hole, and a refining flux is allowed to pass through the flame to promote hatching of the refining flux.

  In Patent Document 4, when the hot metal is dephosphorized by supplying an oxygen source, hot metal having a silicon content of 0.2% by mass or less is used, and the tip of the top blowing lance is directed toward the bath surface of the hot metal. Proposed a dephosphorization process by adding a powdered dephosphorization solvent mainly composed of CaO heated or heated and melted by a flame formed below through a top blowing lance together with a gaseous oxygen source. Has been.

In Patent Document 5, a powdered dephosphorization solvent mainly composed of CaO, SiO ₂ and iron oxide is used as a carrier gas with an oxygen-containing gas as a carrier gas from a central hole arranged in the axial center of the top blowing lance. At the same time, a flame is formed by supplying one or more of hydrocarbon-based fuel gas or liquid fuel from a first peripheral hole disposed around the central hole, and the flame is used for the dephosphorization. There has been proposed a method of heating and melting the solvent and dephosphorizing the hot metal by blowing a refining oxygen-containing gas to the hot metal from the second peripheral hole arranged outside the first peripheral hole.

  Patent Document 6 uses a first upper blow lance having a refining agent supply flow path, a fuel supply flow path, and an oxidizing gas supply flow path for fuel combustion for burning fuel. While forming a flame below the tip of the steel, supply one or more of iron oxide, lime-based solvent, and combustible substance from the refining agent supply flow path to the hot metal in the kneading vehicle together with the inert gas, Dephosphorizing, and then charging the molten iron into the converter, and using a second top blowing lance having a refining oxygen gas supply channel and a fuel supply channel, the fuel supplied from the fuel supply channel A method has been proposed in which a molten steel is produced by decarburizing the hot metal in a converter by supplying a powder medium solvent together with oxygen gas from a refining oxygen gas supply flow path while forming a flame.

JP-A-9-20913 JP 60-67610 A Japanese Patent Laid-Open No. 11-80825 JP 2005-336586 A JP 2007-92158 A JP 2013-209737 A

  However, the above prior art has the following problems.

  That is, in Patent Document 1, the hot metal temperature is increased by adding the carbon source to the generated slag, but the sulfur contained in the carbon source is mixed into the hot metal and the sulfur concentration in the steel is increased. There is a problem. In addition, since it is necessary to ensure the combustion time of the carbon source, there is a problem that the refining time becomes longer, the productivity is lowered, and the manufacturing cost is increased.

  In Patent Document 2, iron scrap is melted while the secondary combustion heat is applied to the iron bath. However, the efficiency of the secondary combustion heat to the iron bath is low, and a lot of secondary combustion heat is applied. If the secondary combustion rate is increased as much as possible, the heat damage of the refractory of the smelting furnace body becomes severe and the problem of a reduction in the furnace life occurs.

  In patent document 3, the upper blowing lance of the quintuple pipe arrange | positioned concentrically is used, that is, from the center part side to the exterior side, 1. 1. A flow path for sub-hole oxygen gas and refining agent; 2. fuel gas flow path; 3. Main hole oxygen gas flow path; 4. cooling water flow path; An upper blow lance composed of a cooling water flow path is used (there are two cooling water flow paths, the cooling water is circulated, one is the water supply flow path and the other is the drainage flow path. ), The flow path of the sub-hole oxygen gas and the refining agent and the flow path of the fuel gas are joined at the tip of the lance to form a combustion flame. Further, the sub-hole oxygen gas and the refining agent are merged at the upper part of the lance. Before the merge, an inert gas such as argon gas is used as the refining agent transfer gas. That is, the substance passing through the flow path of the sub-hole oxygen gas and the refining agent becomes an inert gas such as oxygen gas or argon gas and a refining agent.

  The problem here is that oxygen gas and a refining agent (such as iron oxide, iron ore, and ironworks generated dust) containing a metal and carbon content pass through one channel. That is, when passing through the flow path in the lance, a spark is generated due to friction between the refining agent and the flow path wall (usually made of steel), or oxygen gas and a part of the refining agent react. In addition, there is a risk of heat generation and combustion in the flow path, and there is a problem in the safety management of the equipment. In addition, when performing decarburization processing using this lance, there is a possibility that a metal jump may occur in the nozzle hole for blowing the sub-hole oxygen gas and the refining agent installed at the axial center position of the lance, There is a problem that it hinders operation.

  Patent Documents 4 to 5 use the heat of the flame formed below the tip of the top blowing lance as a heat source in the refining of hot metal. In Document 5, a five-pipe structure is used. In any method, a powder refining agent is supplied using oxygen gas as a carrier gas, and at the same time, this refining agent is heated by a burner flame. However, none of the methods consider the amount of heat of the flame with respect to the supply amount of the refining agent, and it cannot be said that the method is optimized with respect to the heating efficiency of the refining agent and the heat effect on the refractory.

  Patent Document 6 uses the heat of the flame formed below the tip of the top blowing lance as a heat source in the refining of hot metal, and hatching is promoted by heating the powdery refining agent in the flame. It describes that phosphorus efficiency is improved. However, it does not mention the influence of the relationship between the fuel gas flow rate and the powder refining agent supply rate on the dephosphorization efficiency improvement effect, and the relationship between the fuel gas flow rate and the powder refining agent supply rate is optimized. It is hard to say that it has been done.

  The present invention has been made in view of the above circumstances, and an object thereof is to form a flame by combustion of fuel gas below the tip of the upper blowing lance, and supply the molten metal to the molten iron through the upper blowing lance. When performing dephosphorization treatment on hot metal while heating the powdered smelting agent, heat generation efficiency and productivity are excellent without worrying about heat generation and combustion in the flow path of the top blowing lance. An object of the present invention is to provide a hot metal refining method capable of increasing the blending ratio of the cold iron source and obtaining high dephosphorization efficiency without promoting damage to the furnace refractory.

The gist of the present invention for solving the above problems is as follows.
[1] An upper blowing lance having a powdery refining agent supply channel, a fuel gas supply channel, an oxidizing gas supply channel for fuel gas combustion, and an oxidizing gas supply channel for refining separately. The fuel gas is supplied from the fuel gas supply channel, and at the same time the oxidizing gas is supplied from the fuel gas combustion oxidizing gas supply channel to form a flame below the tip of the upper blowing lance, In a hot metal refining method, a powdery refining agent including a decarburizing furnace slag is supplied together with an inert gas from a powder refining agent supply channel toward a hot metal bath surface in a refining vessel, and the hot metal in the refining vessel is dephosphorized. ,
The ratio B / A (kg / MJ) of the powdery refining agent supply rate B (kg / min) to the fuel gas heat supply rate A (MJ / min) is controlled within the range of the following formula (1). A method for refining hot metal, characterized by:
0.80 <B / A <1.50 (1)
In the equation (1), A is a fuel gas consisting of the product of the lower heating value (MJ / Nm ³ ) of the fuel gas supplied from the fuel gas supply flow path and the fuel gas supply flow rate (Nm ³ / min). The heat supply rate (MJ / min), B is the supply rate (kg / min) of the powdery refining agent including the decarburization furnace supplied from the powdery refining agent supply channel.

  According to the present invention, in hot metal refining, a powdered refining agent including a decarburization furnace is supplied from the top blowing lance to the hot metal bath surface in the refining vessel while being heated by a flame formed below the tip of the top blowing lance. In this case, since the ratio B / A of the supply rate B of the powdery refining agent to the heat supply rate A of the fuel gas is controlled within an appropriate range, the powdery refining agent is not heated more than necessary by the flame. In addition, it is possible to obtain an improvement in the dephosphorization efficiency by promoting the hatching of the powdery refining agent while avoiding a decrease in the dephosphorization efficiency due to the powdery refining agent being heated more than necessary. In addition, since the combustion heat of the fuel gas efficiently reaches the hot metal, the mixing ratio of the cold iron source such as iron scrap can be increased, and the heat effect on the refractory material installed in the smelting vessel is Less damage to the refractory can be suppressed.

It is a schematic sectional drawing which shows an example of the converter equipment used when implementing this invention. It is a general | schematic expanded longitudinal cross-sectional view of the upper blowing lance shown in FIG. It is a figure which shows the relationship between ratio B / A and the hot metal phosphorus density | concentration after a dephosphorization process in this invention Examples 1-7 and Comparative Examples 1-28 which use city gas as fuel gas. It is a figure which shows the relationship between ratio B / A and the hot metal phosphorus density | concentration after a dephosphorization process in the present invention examples 51-59 and comparative examples 51-75 which use propane gas as fuel gas.

  Hereinafter, the present invention will be described in detail.

The hot metal produced in the blast furnace is subjected to refining such as desiliconization, dephosphorization, desulfurization, and decarburization to produce molten steel from the hot metal. The desiliconization process, the dephosphorization process, and the desulfurization process are performed as a preliminary process before the decarburization process. These refining processes are carried out in a refining vessel such as a kneading car, hot metal ladle, converter, etc., and a medium solvent containing CaO as a main component or a CaF ₂ -based medium solvent, in addition to these, oxygen gas in the molten iron (industrial pure oxygen) This is done by supplying an oxygen source such as iron oxide. In each of these refining processes, it is known that the reaction efficiency changes depending on the temperature of the hot metal during refining, and each refining process is generally performed in a separate refining vessel. In some cases, a plurality of treatments are performed in the same refining vessel. In this case, refining is performed by changing the composition of the refining agent in accordance with the purpose such as the dephosphorization period and the decarburization period.

For example, the dephosphorization treatment is preferably performed at a relatively low temperature, and a medium solvent mainly composed of CaO and an oxygen source are added, and phosphorus in the hot metal is oxidized with oxygen in the oxygen source to obtain a phosphorus oxide. (P ₂ O ₅ ) is formed, and the formed phosphorous oxide is fixed in a stable form of 3CaO · P ₂ O ₅ (= Ca ₃ (PO ₄ ) ₂ ) in slag produced by the incubation of a CaO-based solvent. Is done by doing.

On the other hand, for the purpose of reducing the environmental burden when manufacturing molten steel from hot metal, reducing the amount of CO ₂ emission, and reducing manufacturing costs, it is required to increase the ratio of the cold iron source to be mixed with hot metal. In order to increase the blending ratio of the cold iron source, heat for melting the cold iron source is necessary, and many studies have been made on heat compensation methods.

  The present inventors include a powdery refining agent supply channel, a fuel gas supply channel, a fuel gas combustion oxidizing gas supply channel for burning fuel gas, and a refining oxidizing gas supply channel. Are separately supplied from the fuel gas supply passage and at the same time the oxidizing gas is supplied from the oxidizing gas supply passage for fuel gas combustion, using an upper blowing lance (hereinafter also referred to as “burner lance”). From the powdery refining agent supply flow path, the powdery refining agent including the decarburizing furnace slag is fed together with an inert gas to the hot metal bath surface in the refining vessel while forming a flame below the top blowing lance. In the hot metal refining method in which the hot metal in the smelting vessel is dephosphorized, the heat receiving efficiency and productivity are excellent, the mixing ratio of the cold iron source such as iron scrap can be increased, and the furnace body Without promoting damage to the refractory, Consider refining methods had dephosphorization efficiency, found refining method shown below.

  Hereinafter, the present invention will be described by taking as an example a case where a converter is used as the refining vessel and the hot metal in the converter is subjected to dephosphorization.

  FIG. 1 is a schematic cross-sectional view showing an example of a converter facility used when carrying out the present invention, and FIG. 2 is a schematic enlarged vertical cross-sectional view of an upper blowing lance 5 shown in FIG. Here, as an example, an upper blowing lance 5 of a six-pipe pipe is shown.

  As shown in FIG. 1, the converter equipment 1 used for the dephosphorization process in the present invention has an outer shell composed of an iron shell 3, and a converter 2 in which a refractory 4 is constructed inside the iron shell 3, An upper blowing lance 5 that is inserted into the converter 2 and is movable in the vertical direction is provided. A top 7 of the converter 2 is provided with an outlet 7 for pouring the molten iron 6 after the dephosphorization process, and a plurality of bottoms for injecting the stirring gas 8 into the bottom of the converter 2. A blowing tuyere 9 is provided. The bottom blowing tuyere 9 is connected to a gas introduction pipe 10.

  A powder refining agent supply pipe 12 for supplying a powder refining agent 11 including a decarburization furnace, together with a carrier gas made of an inert gas such as nitrogen gas or argon gas, and propane Fuel gas supply pipe 13 for supplying fuel gas such as gas, liquefied natural gas, coke oven gas, and city gas, and oxygen gas for burning the supplied fuel gas, oxidizing gas for fuel gas combustion such as air An oxidizing gas supply pipe 14 for fuel gas combustion for supplying gas, a refining oxidizing gas supply pipe 15 for supplying a refining oxidizing gas such as oxygen gas, and a top blowing lance 5 for cooling. A cooling water supply pipe and a drain pipe (not shown) for supplying and discharging the cooling water are connected. FIG. 1 shows an example in which the oxidizing gas for fuel gas combustion and the oxidizing gas for refining are oxygen gases. As the oxidizing gas for refining, oxygen gas, oxygen-enriched air, or a mixed gas of oxygen gas and rare gas is used, but generally oxygen gas is used.

  It is possible to use hydrocarbon-based liquid fuel such as heavy oil or kerosene instead of the fuel gas supplied to the fuel gas supply pipe 13, but there is a possibility of clogging at the nozzle at the outlet of the flow path. Therefore, fuel gas (gaseous fuel) is used in the present invention. If gaseous fuel is used, not only can clogging of nozzles and the like be prevented, but also the supply speed can be easily adjusted, and further, since ignition is easy, misfire can be prevented.

  The other end of the powdery refining agent supply pipe 12 is connected to a dispenser 16 containing the powdery refining agent 11, and the dispenser 16 is connected to a gas supply pipe 17 for conveying the powdery refining agent. The inert gas supplied to the dispenser 16 through the agent conveying gas supply pipe 17 functions as a conveying gas for the powdery refining agent 11 accommodated in the dispenser 16, and the powdery refining agent accommodated in the dispenser 16 11 is supplied to the upper blowing lance 5 through the powdery refining agent supply pipe 12 and can be sprayed from the tip of the upper blowing lance 5 toward the hot metal 6.

  As an example of the upper blow lance 5, an upper blow lance 5 having a six-pipe structure shown in FIG. 2 has a cylindrical lance body 18 and a copper cast lance connected to the lower end of the lance body 18 by welding or the like. The lance body 18 includes six innermost tubes 20, a partition tube 21, an inner tube 22, an intermediate tube 23, an outer tube 24, and an outermost tube 25. It consists of a heavy pipe. The powdery refining agent supply pipe 12 communicates with the innermost pipe 20, the fuel gas supply pipe 13 communicates with the partition pipe 21, the fuel gas combustion oxidizing gas supply pipe 14 communicates with the inner pipe 22, and the refining oxidation. The reactive gas supply pipe 15 communicates with the middle pipe 23, and the cooling water supply pipe and the drain pipe communicate with either the outer pipe 24 or the outermost pipe 25, respectively.

  Therefore, the powdery refining agent 11 passes through the innermost pipe 20 together with the carrier gas, and a fuel gas such as propane gas or city gas passes through the gap between the innermost pipe 20 and the partition pipe 21 to oxidize the fuel gas for combustion. The reductive oxidizing gas passes through the gap between the inner pipe 22 and the inner pipe 23, the gap between the inner pipe 23 and the outer pipe 24, and the outer pipe 24 The gap with the outermost pipe 25 is a cooling water supply channel or a drain channel. One of the gap between the middle pipe 23 and the outer pipe 24 and the gap between the outer pipe 24 and the outermost pipe 25 is a water supply flow path, and the other is a drainage flow path. The cooling water is configured to reverse at the position of the lance tip 19.

  The inside of the innermost pipe 20 communicates with a powdery refining agent injection hole 26 disposed substantially at the axial center of the lance tip 19, and the gap between the innermost pipe 20 and the partition pipe 21 is a powdery refining agent injection hole. 26 is communicated with an annular nozzle or a fuel gas injection hole 27 opening as a plurality of concentric nozzle holes around the periphery of the nozzle 26, and the gap between the partition pipe 21 and the inner pipe 22 is a circle around the fuel gas injection hole 27. The fuel gas combustion oxidizing gas injection hole 28 that opens as an annular nozzle or a plurality of concentric nozzle holes communicates with the gap between the inner tube 22 and the middle tube 23, and the fuel gas combustion oxidizing gas. A plurality of refining oxidizing gas injection holes 29 are provided in the vicinity of the injection holes 28. The powdery refining agent injection hole 26 is a nozzle for spraying the powdery refining agent 11 together with the carrier gas, the fuel gas injection hole 27 is a nozzle for injecting fuel gas, and an oxidizing gas injection hole 28 for fuel gas combustion. Is a nozzle for injecting an oxidizing gas for burning fuel gas, and the refining oxidizing gas injection hole 29 is a nozzle for spraying a refining oxidizing gas.

  That is, the inside of the innermost pipe 20 is a powdery refining agent supply flow path, the gap between the innermost pipe 20 and the partition pipe 21 is a fuel gas supply flow path, and the gap between the partition pipe 21 and the inner pipe 22 is a fuel gas. A combustion oxidizing gas supply channel is formed, and a gap between the inner tube 22 and the intermediate tube 23 is a refining oxidizing gas supply channel. In FIG. 2, the powdery refining agent injection hole 26 is a straight nozzle, and the oxidizing gas injection hole 29 for refining is a Laval nozzle composed of two cones, a portion whose cross section is reduced and a portion where the cross section is enlarged. However, the powdery refining agent injection hole 26 may also have a Laval nozzle shape. The fuel gas injection hole 27 and the oxidizing gas injection hole 28 for fuel gas combustion are straight nozzles that open in the shape of an annular slit, or straight nozzles that have a circular cross section. In the Laval nozzle, the position where the cross section is the narrowest, which is the boundary between the two cones of the reduced portion and the enlarged portion, is called a throat.

  Using the converter equipment 1 having this configuration, the dephosphorization treatment according to the present invention is performed on the hot metal 6 as described below.

First, a cold iron source is charged into the converter 2. The cold iron source used is iron scrap such as slabs and steel plate crops and city scraps generated at steelworks, bullion recovered from slag by magnetic sorting, and cold iron, reduced iron, etc. can do. The blending ratio of the cold iron source is 4.0% by mass or more, preferably 5.0% by mass or more with respect to the total iron source to be charged (mixing ratio of the cold iron source (mass%) = cold). Iron source content x 100 / (molten metal content + cold iron source content)). This is because if the blending ratio of the cold iron source is less than 4.0% by mass, not only the effect of improving the productivity is small but also the effect of reducing the CO ₂ generation amount is small. The upper limit of the blending ratio of the cold iron source does not need to be particularly determined, and the hot metal temperature after the dephosphorization treatment can be added up to an upper limit that can maintain the target range. Before and after the cold iron source is charged, the stirring gas 8 starts to be blown from the bottom blowing tuyere 9.

  After charging the cold iron source into the converter 2, the hot metal 6 is charged into the converter 2. The hot metal 6 to be used can be subjected to dephosphorization treatment regardless of the composition, and may be subjected to desulfurization treatment or desiliconization treatment before the dephosphorization treatment. Incidentally, the main chemical components of the hot metal 6 before the dephosphorization treatment are: carbon: 3.8 to 5.0% by mass, silicon: 0.6% by mass or less, phosphorus: 0.08 to 0.2% by mass, sulfur : About 0.05% by mass or less. Moreover, if the hot metal temperature is in the range of 1200 to 1400 ° C., dephosphorization can be performed without any problem.

  Next, a refining oxidizing gas such as oxygen gas is blown toward the bath surface of the molten iron 6 from the refining oxidizing gas injection hole 29 of the top blowing lance 5 and an inert gas is supplied to the dispenser 16 as a conveying gas. Then, the powdery refining agent 11 including the decarburizing furnace is sprayed from the powdery refining agent injection hole 26 of the upper blowing lance 5 toward the bath surface of the molten iron 6 together with the transfer gas. Before and after the blowing of the powdery refining agent 11, fuel gas is injected from the fuel gas injection hole 27 of the upper blowing lance 5, and oxidation for fuel gas combustion such as oxygen gas is performed from the oxidizing gas injection hole 28 for fuel gas combustion. A sex gas is injected to generate a flame below the upper blowing lance 5.

The decarburization furnace slag is CaO—SiO ₂ —FeO _x slag generated by hot metal decarburization processing in a converter, and can be used as all or part of the powdery refining agent 11. From the viewpoint of promoting hatching of the powdery refining agent 11, the ratio of the decarburization furnace slag in the powdery refining agent 11 is preferably 20% by mass or more, and more preferably 30% by mass or more. As a part of the powdery refining agent 11, quick lime (CaO), limestone (CaCO ₃ ), slaked lime (Ca (OH) ₂ ) or the like can be used. Further, a mixture of quicklime with fluorite (CaF ₂ ) or alumina (Al ₂ O ₃ ) as a hatching accelerator can be used as part of the powdery refining agent 11.

  In the refining of the hot metal 6 using the burner lance 5 performed in this way, the powdered smelting agent 11, iron oxide, and combustible substance are formed in the flame formed by burning the fuel gas and below the tip of the burner lance 5. It is known that the heat of the flame is efficiently transmitted to the powdery refining agent 11 or the like by passing the heat and the like, and thereby it is possible to improve the heat receiving efficiency to the molten iron 6 (see, for example, Patent Document 6). .

  In this burner lance 5, in addition to being able to perform heat compensation of the hot metal 6 in parallel with the progress of refining, since the fuel gas does not contain sulfur, the hot metal of sulfur which is a problem in the heat compensation by the carbon source. Mixing in and refining time can be avoided. In addition, since the heat of combustion of the fuel gas can be efficiently supplied to the molten iron 6 by passing the powdery refining agent 11 serving as a heat transfer medium through the flame, secondary combustion that has been studied as a conventional heat compensation technique. Compared with the method of increasing the rate, thermal compensation can be performed without increasing the thermal damage of the refractory in the smelting vessel. Furthermore, in the present invention, since an inert gas is used as the conveying gas for the powdery refining agent 11 including the decarburization furnace, the combustible substance contained in the powdery refining agent 11 in the flow path of the burner lance 5. The problem of burning can be avoided.

  In addition to these advantages, in the refining of the hot metal 6 using the combustion heat by the burner lance 5, there is an advantage that the dephosphorization efficiency can be improved. This is because heating of the powdery refining agent 11 in a flame promotes the hatching of the powdery refining agent 11, that is, the slag having an excellent ability to absorb phosphorous oxide is formed at an early stage. This is because phosphorus efficiency is improved (see, for example, Patent Document 6). However, since the dephosphorization reaction is an exothermic reaction, the hot metal temperature and the slag temperature in the dephosphorization process are advantageously lower, for example, about 1200 to 1400 ° C., and the hot metal temperature is excessively increased. It is known that is desirable for increasing the amount of dissolution of the cold iron source, but not desirable for the dephosphorization reaction.

  In particular, since the decarburization furnace contains usually about 1 to 2% by mass of phosphorus as a phosphorus oxide, the present inventors can use the decarburization furnace used as the powder refining agent 11 depending on the refining conditions. It was thought that the dephosphorization efficiency could reduce the dephosphorization efficiency.

  Therefore, the inventors of the present invention have heated the powder refining agent 11 including the decarburization furnace soot by the burner lance 5 to improve the dephosphorization efficiency by promoting the hatching, while the temperature rise of the powder refining agent 11 removes the dephosphorization. It is thought that this becomes a factor of reducing the efficiency, and the supply rate B (kg / min) of the powdery refining agent 11 supplied from the powdery refining agent supply pipe 12 of the burner lance 5 and the heat supply rate A (MJ) of the burner lance 5 The ratio B / A (kg / MJ) to the dephosphorization efficiency was investigated by changing the fuel gas type, the fuel gas flow rate, and the supply speed of the powdery refining agent 11 (Examples described later) 1 and 2). The heat supply rate A (MJ / min) at the burner lance 5 is obtained by the following equation (3).

A = Q _L × F (3)
However, in the formula (3), A is the heat supply rate (MJ / min), Q _L is the lower heating value per 1 m ³ (MJ / Nm ³ ) in the standard state of the fuel gas, and F is in the standard state of the fuel gas. Supply flow rate (Nm ³ / min). Here, the lower heating value of the fuel gas is a value obtained by subtracting the latent heat of water vapor generated from hydrogen or originally contained water in the fuel gas from the standard combustion heat of the fuel gas based on 25 ° C. and 1 atm. This corresponds to the amount of heat that can be used for heating the powder in practice.

  As a result, as shown in FIGS. 3 and 4, the supply rate B (kg / min) of the powdery refining agent 11 injected from the powdery refining agent injection hole 26, and the heat supply rate A (MJ) at the burner lance 5. / Min), the dephosphorization efficiency changes according to the ratio B / A (kg / MJ), and by controlling the ratio B / A within the range of the following formula (1), the dephosphorization efficiency can be increased. I found it possible.

0.80 <B / A <1.50 (1)
When the ratio B / A is 0.80 or less, the supply rate B of the powdery refining agent 11 including the decarburization furnace is relatively small with respect to the heat supply rate A by the burner lance 5, so that the powdery refining agent 11 The temperature of the smelting agent 11 becomes excessively high, and the dephosphorization efficiency is reduced by increasing the temperature of the powdery smelting agent 11 while the dephosphorization efficiency is reduced by increasing the temperature of the smelting agent 11, and the dephosphorization improving effect is reduced. It is thought to go. On the other hand, when the ratio B / A is 1.50 or more, the supply rate B of the powdery refining agent 11 including the decarburization furnace slag is relatively higher than the heat supply rate A of the burner lance 5, so that the powdery refining It is considered that the temperature of the agent 11 is low and the hatching promoting effect is small, and the dephosphorization efficiency improving effect is reduced.

  In addition, when using powder having thermal decomposability such as calcium carbonate powder as the powdery refining agent 11, the temperature of the powdery refining agent 11 is lowered due to heat of decomposition. It is considered that the ratio B / A range in which the dephosphorization efficiency improvement effect is obtained shifts to a lower value side in an environment where the dephosphorization occurs.

  As described above, according to the present invention, since the ratio B / A is controlled within an appropriate range, the powdery refining agent 11 is not heated more than necessary by the flame. While avoiding a decrease in the dephosphorization efficiency due to heating more than necessary, it is possible to enjoy a high dephosphorization efficiency improvement effect by promoting the hatching of the powdery refining agent 11.

  In addition, although the said description demonstrated by the case where the converter 2 was used as a refining container, even if it uses a kneading car and a hot metal ladle as a refining container, this invention can be implemented without any problem.

A furnace capacity of 330 tons, which is the same type as the converter equipment shown in FIG. 1, is used, and a cold iron source and hot metal are charged into this converter, and city gas (low heating value) is used as fuel gas. Q _L = 40.6 MJ / Nm ³ ), changing the fuel gas supply flow rate and the powder refining agent (mixture of quick lime and decarburizer furnace) to perform dephosphorization of hot metal (Invention Examples 1 to 7, Comparative Examples 1 to 28).

  In the present invention examples 1 to 7 and comparative examples 1 to 28, the used top blowing lance has a six-pipe structure similar to the top blowing lance shown in FIG. A refining agent supply channel, a fuel gas supply channel, an oxidizing gas supply channel for fuel gas combustion, an oxidizing gas supply channel for refining, and two cooling water channels for cooling water supply and drainage are configured in this order. . Except for the cooling water flow path, it has a nozzle that opens vertically downward or diagonally downward at the top of the top blowing lance, and the powder refining agent comes from the circular straight refining agent injection hole at the center of the lance tip, and the fuel gas is From the annular (ring-shaped) slit type fuel gas injection hole, the oxygen gas for fuel gas combustion is from the annular (ring-shaped) slit type oxidizing gas injection hole for fuel gas combustion, and the refining oxygen gas is concentrically A plurality of arranged Laval nozzle type oxidizing gas injection holes were supplied into the furnace.

In Invention Examples 1-7 and Comparative Examples 1-28, after 46.2 tons of cold iron source was charged into the converter, the hot metal temperature: 1300 ° C., silicon concentration: 0.35 mass%, phosphorus concentration; After charging 283.8 tons of hot metal having a mass of 14% by mass and a carbon concentration of 4.4% by mass, the upper blowing lance is lowered until the tip of the hot metal is 2500 mm from the surface of the hot metal in the stationary state ( Lance height = 2500 mm), then, after adding massive quick lime from the top of the 3 ton furnace, premixed quick lime powder and decarburization furnace soot at a mass ratio of 1: 2 (= powder refining agent), city Gas (comparative examples 1-5, nitrogen gas instead of city gas), fuel gas combustion oxygen gas (comparative examples 1-5, nitrogen gas instead of fuel gas combustion oxygen gas), refining oxygen gas, While blowing toward the hot metal bath surface through the blowing lance, Nitrogen gas was blown in dephosphorization in molten pig iron as the stirring gas. In addition, the composition of the decarburization furnace was 40% by mass for CaO and 12% by mass for SiO ₂ .

The supply flow rate of the refining oxygen gas was 22,000 Nm ³ / hr. Using nitrogen gas as the bottom-blown agitation gas and carrier gas, the flow rate was respectively 30 Nm ³ / min, and 25 Nm ³ / min. All refining times were fixed at 15 minutes.

The city gas flow rate is 10-60 Nm ³ / min, and the oxygen gas flow rate for fuel gas combustion is 2.2 times the city gas flow rate (22-132 Nm ³ / min) in order to completely burn the city gas. It was. Further, the supply rate of the powdery refining agent was 200 to 1000 kg / min, and the total supply amount of the powdery refining agent was 3 tons at any supply rate. Simultaneously with the start of supply of oxygen gas for refining, supply of city gas, oxygen gas for fuel gas combustion and powdery refining agent is started, and when the total supply amount of powdery refining agent reaches 3 tons, Supply of oxygen gas for fuel gas combustion and powdery refining agent was stopped.

In addition, after stopping supply of city gas, fuel gas combustion oxygen gas, and powdery refining agent, nitrogen gas was supplied so that splash or the like would not enter each supply flow path of the top blowing lance. During the period from the end of supply of city gas, oxygen gas for fuel gas combustion and powdered refining agent to the end of blowing, nitrogen gas is 10 Nm ³ / min in the fuel gas supply channel, and the oxidizing gas supply channel for fuel gas combustion is Nitrogen gas 22 Nm ³ / min and nitrogen gas 25 Nm ³ / min were supplied to the powdery refining agent supply channel.

  Table 1 shows the city gas flow rate, heat supply rate A, powder refining agent supply rate B including decarburization furnace B, ratio B / A, and dephosphorization treatment in Invention Examples 1 to 7 and Comparative Examples 1 to 28. The hot metal phosphorus concentration etc. are shown later. FIG. 3 shows the relationship between the ratio B / A and the hot metal phosphorus concentration after the dephosphorization treatment in Invention Examples 1 to 7 and Comparative Examples 1 to 28.

  As shown in Examples 1 to 7 of the present invention, in order to stably reduce the phosphorus concentration in the hot metal after the dephosphorization treatment, the ratio B / A should be set to a condition of more than 0.80 and less than 1.50. I found it necessary. This is considered to reflect that the dephosphorization efficiency is improved by promoting the hatching of the powdery refining agent when the powdery refining agent is appropriately heated by the flame.

  On the other hand, the phosphorus concentration in the hot metal after the dephosphorization treatment under the condition of not supplying the city gas shown in Comparative Examples 1 to 5 is such that the ratio B / A shown in Invention Examples 1 to 7 is 0.80 and less than 1.50. It was confirmed that the concentration was higher than the phosphorus concentration in the hot metal after the dephosphorization treatment under the above conditions. This is considered to reflect that the powder refining agent was not heated and the effect of improving the dephosphorization efficiency due to the promotion of hatching of the powder refining agent was not obtained.

  Further, as shown in Comparative Examples 6 to 19 and Comparative Examples 22, 23, 24, 27, and 28, the phosphorus concentration in the hot metal after the dephosphorization treatment when the ratio B / A is 0.80 or less is the present invention. It was confirmed that the ratio B / A shown in Examples 1 to 7 was higher than the phosphorus concentration in the hot metal after the dephosphorization treatment under the condition of 0.80 and less than 1.50. This is because the powder refining agent supply rate B is smaller than the heat supply rate A, and the temperature of the powder refining agent is higher than the dephosphorization efficiency improving effect by promoting the hatching of the heated powder refining agent. This is considered to reflect that the dephosphorization efficiency lowering effect was greater.

  Furthermore, as shown in Comparative Examples 20, 21, 25, and 26, the phosphorus concentration in the hot metal after the dephosphorization treatment when the ratio B / A is 1.50 or more is the ratio shown in Examples 1 to 7 of the present invention. It was confirmed that the B / A was higher than the phosphorus concentration in the hot metal after the dephosphorization treatment under the condition of 0.80 and less than 1.50. This is because the powder refining agent supply rate B is larger than the heat supply rate A, the temperature of the heated powder refining agent is low, and the effect of improving the dephosphorization efficiency by promoting the hatching of the powder refining agent is small. It is thought that this is reflected.

As in Example 1, a furnace capacity of 330 tons was used in the same manner as the converter equipment shown in FIG. 1, and a cold iron source and hot metal were charged into the converter, and the fuel gas Propane gas (low calorific value Q _L = 91.0 MJ / Nm ³ ), and changing the fuel gas supply flow rate and powder refining agent (mixture of quick lime and decarburization furnace), The hot metal was dephosphorized (Invention Examples 51-59, Comparative Examples 51-75).

  In the inventive examples 51 to 59 and the comparative examples 51 to 75, the used top blowing lance is of a six-pipe structure like the top blowing lance shown in FIG. A refining agent supply channel, a fuel gas supply channel, an oxidizing gas supply channel for fuel gas combustion, an oxidizing gas supply channel for refining, and two cooling water channels for cooling water supply and drainage are configured in this order. . Except for the cooling water flow path, it has a nozzle that opens vertically downward or diagonally downward at the top of the top blowing lance, and the powder refining agent comes from the circular straight refining agent injection hole at the center of the lance tip, and the fuel gas is From the annular (ring-shaped) slit type fuel gas injection hole, the oxygen gas for fuel gas combustion is from the annular (ring-shaped) slit type oxidizing gas injection hole for fuel gas combustion, and the refining oxygen gas is concentrically A plurality of arranged Laval nozzle type oxidizing gas injection holes were supplied into the furnace.

In Invention Examples 51-59 and Comparative Examples 51-75, after 46.2 tons of cold iron source was charged into the converter, the hot metal temperature: 1300 ° C., silicon concentration; 0.35 mass%, phosphorus concentration; After charging 283.8 tons of hot metal having a mass of 14% by mass and a carbon concentration of 4.4% by mass, the upper blowing lance is lowered until the tip of the hot metal is 2500 mm from the surface of the hot metal in the stationary state ( Lance height = 2500 mm), and then a mixture of quick lime powder and decarburization furnace pre-mixed at a mass ratio of 1: 2 (= powder refining agent) and propane Gas (nitrogen gas instead of propane gas in Comparative Examples 51 to 55), oxygen gas for fuel gas combustion (nitrogen gas instead of fuel gas combustion oxygen gas in Comparative Examples 51 to 55), refining oxygen gas, Sprayed onto the hot metal bath surface via a blowing lance While, nitrogen gas was blown in dephosphorization in molten pig iron as the stirring gas from the bottom tuyeres. The composition of the decarburization furnace was 40% by mass for CaO and 12% by mass for SiO ₂ .

The supply flow rate of the refining oxygen gas was 22,000 Nm ³ / hr. Using nitrogen gas as the bottom-blown agitation gas and carrier gas, the flow rate was respectively 30 Nm ³ / min, and 25 Nm ³ / min. All refining times were fixed at 15 minutes.

The flow rate of propane gas is 5 to 25 Nm ³ / min, and the oxygen gas flow rate for fuel gas combustion is 5 times the flow rate of propane gas (25 to 125 Nm ³ / min) in order to completely burn propane gas. . Further, the supply rate of the powdery refining agent was 200 to 1000 kg / min, and the total supply amount of the powdery refining agent was 3 tons at any supply rate. Simultaneously with the start of the supply of refining oxygen gas, the supply of propane gas, fuel gas combustion oxygen gas and powder refining agent is started, and when the total supply amount of powder refining agent reaches 3 tons, propane gas, Supply of oxygen gas for fuel gas combustion and powdery refining agent was stopped.

Note that after the supply of propane gas, fuel gas combustion oxygen gas, and powdery refining agent was stopped, nitrogen gas was supplied so that splash or the like did not enter the supply channels of the top blowing lance. During the period from the end of the supply of propane gas, oxygen gas for fuel gas combustion and powdered smelting agent to the end of blowing, nitrogen gas is 10 Nm ³ / min in the fuel gas supply channel, and the oxidizing gas supply channel for fuel gas combustion is Nitrogen gas 22 Nm ³ / min and nitrogen gas 25 Nm ³ / min were supplied to the powdery refining agent supply channel.

  Table 2 shows the propane gas flow rate, heat supply rate A, powdery refining agent supply rate B including decarburization furnace, ratio B / A, and dephosphorization treatment in Inventive Examples 51-59 and Comparative Examples 51-75. The hot metal phosphorus concentration etc. are shown later. FIG. 4 shows the relationship between the ratio B / A and the hot metal phosphorus concentration after the dephosphorization treatment in Inventive Examples 51-59 and Comparative Examples 51-75.

  As shown in Examples 51 to 59 of the present invention, in order to reduce the phosphorus concentration in the hot metal after the dephosphorization treatment, the ratio B / A needs to be in the range of 0.80 to less than 1.50. I understood it. This is considered to reflect that the dephosphorization efficiency is improved by promoting the hatching of the powdery refining agent when the powdery refining agent is appropriately heated by the flame.

  On the other hand, the phosphorus concentration in the hot metal after dephosphorization under the condition where propane gas is not supplied as shown in Comparative Examples 51 to 55 is such that the ratio B / A shown in Invention Examples 51 to 59 is more than 0.80 and less than 1.50. It was confirmed that the concentration was higher than the phosphorus concentration in the hot metal after the dephosphorization treatment under the above conditions. This is considered to reflect that the powder refining agent was not heated and the effect of improving the dephosphorization efficiency due to the promotion of hatching of the powder refining agent was not obtained.

  Further, as shown in Comparative Examples 56 to 68 and Comparative Examples 70, 71, 74, and 75, the phosphorus concentration in the hot metal after the dephosphorization treatment when the ratio B / A is 0.80 or less is Example 51 of the present invention. It was confirmed that the ratio B / A shown in .about.59 was higher than the phosphorus concentration in the hot metal after the dephosphorization treatment under the condition of 0.80 and less than 1.50. This is because the powder refining agent supply rate B is smaller than the heat supply rate A, and the temperature of the powder refining agent is higher than the dephosphorization efficiency improving effect by promoting the hatching of the heated powder refining agent. This is considered to reflect that the dephosphorization efficiency lowering effect was greater.

  Furthermore, as shown in Comparative Examples 69, 72, and 73, the phosphorus concentration in the hot metal after the dephosphorization treatment when the ratio B / A is 1.50 or more is the ratio B / A shown in the inventive examples 51 to 59. It was confirmed that A is higher than the phosphorus concentration in the hot metal after the dephosphorization treatment under the condition of 0.80 and less than 1.50. This is because the powder refining agent supply rate B is larger than the heat supply rate A, the temperature of the heated powder refining agent is low, and the effect of improving the dephosphorization efficiency by promoting the hatching of the powder refining agent is small. It is thought that this is reflected.

DESCRIPTION OF SYMBOLS 1 Converter equipment 2 Converter 3 Iron skin 4 Refractory 5 Top blowing lance 6 Hot metal 7 Outlet 8 Stirring gas 9 Bottom blowing tuyere 10 Gas introduction pipe 11 Powder refiner 12 Powder refiner supply pipe 13 Fuel gas Supply pipe 14 Oxidizing gas supply pipe for fuel gas combustion 15 Refining oxidizing gas supply pipe 16 Dispenser 17 Gas supply pipe for conveying powdery refining agent 18 Lance main body 19 Lance tip 20 Innermost pipe 21 Partition pipe 22 Inner pipe 23 Medium Pipe 24 Outer pipe 25 Outermost pipe 26 Powdery refining agent injection hole 27 Fuel gas injection hole 28 Oxidizing gas injection hole for fuel gas combustion 29 Oxidizing gas injection hole for refining

Claims (1)

Using an upper blowing lance having a powdery refining agent supply channel, a fuel gas supply channel, an oxidizing gas supply channel for fuel gas combustion, and an oxidizing gas supply channel for refining separately, While supplying the fuel gas from the fuel gas supply flow path, supplying the oxidizing gas from the fuel gas combustion oxidizing gas supply flow path to form a flame below the tip of the upper blowing lance, the powdery refining agent In the hot metal refining method, the powder refining agent including the decarburization furnace is supplied from the supply flow path to the hot metal bath surface in the refining vessel together with the inert gas, and the hot metal in the refining vessel is dephosphorized.
The ratio B / A (kg / MJ) of the powdery refining agent supply rate B (kg / min) to the fuel gas heat supply rate A (MJ / min) is controlled within the range of the following formula (1). A method for refining hot metal, characterized by:
0.80 <B / A <1.50 (1)
In the equation (1), A is a fuel gas consisting of the product of the lower heating value (MJ / Nm ³ ) of the fuel gas supplied from the fuel gas supply flow path and the fuel gas supply flow rate (Nm ³ / min). The heat supply rate (MJ / min), B is the supply rate (kg / min) of the powdery refining agent including the decarburization furnace supplied from the powdery refining agent supply channel.

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