JP5870584B2 - Hot metal dephosphorization method - Google Patents

Description

  The present invention relates to a method of dephosphorizing hot metal contained in a refining vessel such as a converter-type refining vessel, and more specifically, dephosphorizing a biomass-derived carbon source having an ash content of 9% by mass or less. The present invention relates to a hot metal dephosphorization method that is added to the hot metal in the hot metal while suppressing decarburization of the hot metal.

In recent years, dephosphorization treatment (also referred to as “preliminary dephosphorization treatment”) is performed in advance in the hot metal stage, and after removing a certain amount of phosphorus in the hot metal, the hot metal is charged into a converter and decarburized in the converter. Steelmaking methods for refining have been developed. In this case, the hot metal dephosphorization treatment uses a hot metal holding container such as a torpedo car or hot metal ladle or a refining furnace such as a converter as a refining container, and uses a CaO-based dephosphorization medium solvent, oxygen gas, and oxygen such as solid iron oxide. In the slag formed by adding phosphorus to the hot metal, oxidizing the phosphorus in the hot metal with an oxygen source, and oxidizing the phosphorus oxide (P ₂ O ₅ ) generated by the oxidation reaction with a CaO-based dephosphorization medium solvent And removing phosphorus in the hot metal.

  Thus, in the hot metal dephosphorization treatment using the CaO-based dephosphorization medium solvent, the hot metal is oxidized and refined by an oxygen source, so the so-called decarburization reaction in which the carbon in the hot metal is oxidized and reduced is called dephosphorization reaction. It happens in parallel. The oxidation heat of carbon in hot metal is used for melting iron scrap and Mn ore, for example, as a heat source for converter refining in the subsequent process. Therefore, the progress of decarburization reaction in the dephosphorization treatment of hot metal is the next process. This will lead to a lack of heat.

  As a means for compensating for this heat shortage, many methods have been proposed in which a carbon source such as coke is added to the hot metal during the dephosphorization process to supplement the carbon in the hot metal or the combustion heat of the carbon source is applied to the hot metal. ing. For example, in Patent Document 1, a carbon source is blown into hot metal during the dephosphorization treatment, and carbon is precipitated in coexisting slag by setting the amount of carbon in the hot metal to a saturated concentration or more, and an oxygen source is added to the slag. There has been proposed a dephosphorization method in which carbon deposited by blowing is burned to improve the thermal margin. However, in this method, the carbon source that precipitates in the slag is burned by the oxygen source that blows into the slag, so if the precipitated carbon source cannot be burned sufficiently, the carbon source remains in the slag, There is a possibility that FeO in the slag is reduced by this carbon source, and the oxygen potential of the slag is lowered to inhibit the dephosphorization reaction.

  Further, in Patent Document 2, when adding hot metal gas to a hot metal charged in a top-bottomed converter type refining vessel and adding CaO as a dephosphorization medium solvent, oxygen gas is blown up to dephosphorize the hot metal. A dephosphorization method has been proposed in which a carbon source is added from above the converter-type refining vessel and oxygen gas equivalent to the amount of the added carbon source is blown to accelerate the hatching of CaO by the combustion heat of the carbon source. Yes. However, in this method, the amount of oxygen gas added increases in proportion to the amount of carbon source added. Therefore, when a large amount of carbon source is to be used effectively, the oxygen gas blowing time becomes longer and the oxygen gas is removed. The processing capacity of the phosphorus facility is reduced. Furthermore, since the dephosphorizing agent CaO and the carbon source are added from above the refining vessel and added, the location of the dephosphorization reaction and the location of the carburization reaction are the same, and the added carbon source There is a possibility that the dephosphorization reaction is hindered.

JP-A-9-20912 JP 2002-69522 A

  The present invention has been made in view of the above circumstances, and the object of the present invention is to prevent dephosphorization reaction from being hindered when dephosphorizing hot metal using oxygen gas and a CaO-based dephosphorization medium solvent. And it is providing the dephosphorization processing method which can suppress decarburization of hot metal efficiently, without reducing the dephosphorization processing capability.

  In order to solve the above problems, the present inventors used a hot metal ladle and a converter type refining vessel as a refining vessel, sprayed oxygen gas from the top blowing lance onto the hot metal surface, and supplied a CaO-based dephosphorization medium solvent. The hot metal dephosphorization test was conducted under various conditions. The test results will be described below.

The dephosphorization reaction at the time of dephosphorizing the hot metal using a gaseous oxygen source such as oxygen gas or a solid oxygen source such as mill scale or iron ore proceeds according to the following formula (1).
2P + 5FeO + 3CaO = 3CaO · P ₂ O ₅ + 5Fe (1)
The reason for supplying a gaseous oxygen source such as oxygen gas or a solid oxygen source such as iron oxide as the oxygen source in this dephosphorization treatment is to generate FeO in the second term on the left side of equation (1) in the slag. .

However, since an oxygen source such as oxygen gas or iron oxide is supplied to the hot metal, the decarburization reaction shown in the following formula (2) also proceeds, and the carbon concentration in the hot metal after the dephosphorization process is lowered.
C + 1 / 2O ₂ = CO (2)
Therefore, as a means for compensating for the heat margin, the inventors investigated to increase the carbon concentration in the hot metal by adding a carbon source (also referred to as “charcoal”) to the hot metal.

However, if the method of adding the carbon source is not appropriate, the added carbon source may reduce FeO necessary for the dephosphorylation reaction and the dephosphorization reaction may be hindered by the reaction shown in the following formula (3). is there. That is, it is necessary to employ an efficient carburizing method that does not proceed with the reduction reaction of the formula (3) while the dephosphorization reaction of the formula (1) proceeds.
FeO + C = Fe + CO (3)
In order to cope with this, the present inventors have studied to separate the dephosphorization reaction site and the carburization reaction site in the refining vessel. As a result, the following events were found.

That is, FeO is generated abundantly at the collision position (referred to as “fire point”) of the oxygen gas supplied by blowing from the upper blow lance on the molten metal surface to form P ₂ O ₅ , and toward this fire point. If the powdered CaO-based dephosphorization medium solvent is sprayed and added, the CaO-based dephosphorization medium solvent is directly supplied to the place where P ₂ O ₅ is abundantly formed. The dephosphorization reaction shown proceeds efficiently. That is, by adding the powdered CaO-based dephosphorization medium solvent to the fire point and adding it, the fire point can be made the main place of the dephosphorization reaction.

  On the other hand, the carbon source basically needs to be supplied to other than the fire point. When a converter-type smelting vessel is used as a smelting vessel, the carbon source is placed in the vessel from above the converter-type smelting vessel, so that when the input carbon source falls, It collides with the upper blowing lance upright at the center position and disperses, and the falling position of the carbon source is dispersed in the refining vessel. In this case, although a carbon source that falls to the hot spot is also generated, the area ratio of the fire spot in the horizontal section in the refining vessel is small, and most of the carbon source falls to a position different from the hot spot and is added at that position. Since the charcoal reaction proceeds, the influence of the carbon source addition on the dephosphorization reaction at the fire point can be extremely reduced.

  That is, when performing dephosphorization of hot metal using a converter type refining vessel, by adding a powdered CaO-based dephosphorization medium solvent to the hot spot and adding a carbon source on top, The main place of the carburization reaction is a place other than the fire point, and the place of the dephosphorization reaction and the place of the carburization reaction are separated, so that the dephosphorization reaction can proceed efficiently. Furthermore, the carbon source that falls outside the hot spot dissolves in the hot metal with almost no combustion by the oxygen gas, so oxygen gas for burning the carbon source is not necessary, and the amount of oxygen gas to be supplied is added to the carbon source. There is no need to increase the amount. Therefore, it is not necessary to extend the dephosphorization time, and the dephosphorization capacity is not reduced.

  On the other hand, when a hot metal holding vessel such as a hot metal ladle or torpedo car is used as a refining vessel, a chute or blowing lance for introducing a carbon source is placed on the hot metal bath surface in the refining vessel as compared with a converter type refining vessel. The supply of the carbon source other than the fire point can be easily realized by adjusting the position of the chute for charging the carbon source and the blowing lance.

  In addition, as the test was repeated, it was found that the lower the ash content of the carbon source to be added, the faster the carbon source dissolved in the hot metal and the less the influence on the dephosphorization reaction. This is because the carbon source having a high dissolution rate in the hot metal dissolves in the hot metal immediately after being added to the hot metal, so that the reduction of FeO by the added carbon source is suppressed, or the ratio of reacting with oxygen gas is high. This is because the target amount of carburization can be ensured with a small addition amount.

  In other words, when a hot metal ladle or torpedo car is used as a refining vessel, the carbon source is added without adjusting the carbon source addition position unless the carbon source is intentionally added to the fire point. It has been found that even when a part of the carbon source is added to the hot spot, when a carbon source having a low ash content is used, it can be carburized without inhibiting the dephosphorization reaction. The ash content in the carbon source is about 18% by mass for soil graphite and about 11% by mass for coke, which are usually used as a carburizing material in a refining furnace, and 9% by mass for biomass coal derived from palm palm. It is as follows. That is, it was found that biomass charcoal with a low ash content is optimal as the carbon source to be added. From these results, in the present invention, it is an essential condition that a carbon source derived from biomass and having an ash content of 9% by mass or less is used as a carburizing material.

  In addition, as the test is repeated, the carbon source can be quickly dissolved in the hot metal, and the carbon source that reacts with oxygen gas can be reduced by rapidly dissolving the carbon source. It is understood that it is preferable to continuously charge the carbon source even if the total amount of the carbon source is the same, because it can be added in a relatively uniform manner in the converter type refining vessel. It was. However, “continuously charged” includes not only the case of continuous addition but also the case of intermittently charging the carbon source at short time intervals of about 2 minutes or less.

  It was also found that the start timing of carbon source input affects the carbon source yield. In other words, since a certain amount of time is required for the carbon source to dissolve in the hot metal, even if the carbon source is added at the end of the dephosphorization process, the carbon source does not completely melt into the hot metal, To remain. Accordingly, it has been found that it is preferable to start charging the carbon source by the first half of the dephosphorization treatment.

  In order to accelerate the dephosphorization reaction, a CaO-based dephosphorization medium added with a fluorine source such as fluorite, which is a CaO hatching accelerator, is generally used. When the hot metal is dephosphorized by spraying the solvent for dephosphorization toward the fire point, the hatching of the solvent for CaO dephosphorization is promoted, that is, without adding a fluorine source such as fluorite, It has also been confirmed that even if a simple substance such as quick lime (CaO) is used as a CaO-based dephosphorization medium solvent, dephosphorization treatment equivalent to the conventional one can be performed. In this case, it was found that the basic unit of use of the CaO-based dephosphorization medium solvent was significantly reduced by promoting the hatching of the CaO-based dephosphorization medium solvent. The oxygen gas in the present invention is industrially referred to as pure oxygen gas, and gas containing about several percent by volume of nitrogen gas or the like is also included in the oxygen gas in the present invention.

This invention is made | formed based on these knowledge, The summary is as follows.
(1) While blowing oxygen gas through the top blowing lance toward the hot metal bath surface accommodated in the refining vessel, spraying a CaO-based dephosphorization solvent toward the oxygen gas blowing surface of the hot metal bath surface A method for dephosphorizing hot metal, wherein a carbon source derived from biomass and having an ash content of 9% by mass or less is added to the refining vessel when the hot metal is dephosphorized.
(2) The refining vessel is a converter-type refining vessel, and the carbon source is collided with an upper blowing lance standing upright in the converter-type refining vessel, and the carbon source is brought into the converter-type refining vessel by this collision. The hot metal dephosphorization method according to (1) above, wherein the hot metal is added after being dispersed.
(3) The carbon source is any one or more of biomass charcoal derived from palm coconut shell, biomass charcoal derived from palm palm empty bunch, and biomass charcoal derived from palm palm trunk, (1) or the hot metal dephosphorization method according to (2) above.
(4) The hot metal dephosphorization method according to any one of (1) to (3) above, wherein the carbon source is continuously added.
(5) The above (1) to (4), characterized in that the addition start timing of the carbon source into the refining vessel is until a time point at which half of the processing time required for the dephosphorization processing has elapsed. 4. The hot metal dephosphorization method according to any one of the above.

  According to the present invention, the carbon source derived from biomass and having an ash content of 9% by mass or less is added while spraying the CaO-based dephosphorization medium solvent on the fire point, so that the biomass-derived ash content is 9%. A carbon source having a mass% or less dissolves immediately in the hot metal because of its high dissolution rate in the hot metal, and the hot metal can be added quickly and efficiently without hindering the dephosphorization reaction and without degrading the dephosphorization capacity. Charging is realized. In addition, when the carbon source is added to the refining vessel in a dispersed manner, the location of the dephosphorization reaction and the location of the carburization reaction in the refining vessel are separated, and the hot metal is carburized without further inhibiting the dephosphorization reaction. It becomes possible to do. That is, according to the present invention, it is possible to efficiently suppress the decarburization of the hot metal, and as a result, it is possible to significantly increase the thermal margin of the hot metal as compared with the conventional case. It is possible to reduce the mixture ratio of hot metal and increase the amount of manganese ore added, which not only saves resources and energy, but also stabilizes converter decarburization operations. It has a beneficial effect.

It is a schematic sectional drawing of the converter type refining equipment used when implementing the hot metal dephosphorization processing method concerning this invention. It is a figure which shows the correlation with the amount of decarburization in the example of this invention, and a comparative example, and the amount of dephosphorization. It is a figure which shows the correlation with the ash content in the carbon source in this invention example and a comparative example, and the amount of decarburization. In the example of this invention, it is a figure which shows the relationship between the value which divided the addition start time of the carbon source by the dephosphorization processing time, and the amount of decarburization.

  Hereinafter, a case where the present invention is implemented in a converter type refining facility will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of a converter-type refining equipment used when carrying out the hot metal dephosphorization method according to the present invention.

  As shown in FIG. 1, the converter-type refining equipment 1 used in the hot metal dephosphorization process according to the present invention has an outer shell formed of an iron shell 4, and a refractory 5 is enforced inside the iron shell 4. A furnace body 2 and a steel top blowing lance 3 which is inserted into the interior space of the furnace body 2 and is movable in the vertical direction are provided. At the upper part of the furnace body 2, a hot water outlet 6 is provided for discharging the molten iron 15 accommodated after refining, and a bottom blowing tuyere 7 for blowing the stirring gas 18 into the furnace bottom of the furnace body 2. Is provided. The bottom blowing tuyere 7 is connected to a gas introduction pipe 8. An oxygen gas pipe 9 is connected to the top blowing lance 3, and oxygen gas is supplied from the top blowing lance 3 to the inside of the furnace body 2 through the oxygen gas pipe 9 at an arbitrary flow rate. .

  Above the furnace main body 2, the carbon source 21 derived from biomass and having an ash content of 9% by mass or less is charged into the furnace main body 2, that is, the carbon source 21 is accommodated in the furnace main body 2. A carbon source addition device 20 is installed on top of the hot metal 15 and slag 16 for addition. As the carbon source addition device 20, for example, a conventional raw material supply device including a hopper, a chute, a weighing machine, a cutting device and the like can be used.

  The top blowing lance 3 is connected to a dispenser 11 that contains a CaO-based dephosphorizing agent 17 through an additive for transferring the anti-phosphorus agent 19. On the other hand, the dispenser 11 is branched from the oxygen gas pipe 9. An oxygen gas pipe 9A and a nitrogen gas pipe 10 are connected. In other words, the oxygen gas and nitrogen gas supplied to the dispenser 11 function as a transport gas for the CaO-based dephosphorizing agent 17 contained in the dispenser 11, and blown upward through the additive agent transfer pipe 19. It is configured so that the CaO-based dephosphorizing agent 17 can be sprayed and supplied (also referred to as “projection”) from the tip of the lance 3 toward the surface of the hot metal bath in the furnace body where the oxygen gas is sprayed. Has been.

  The oxygen gas pipes 9 and 9A are respectively provided with flow rate adjusting valves 12 and 13, and the nitrogen gas pipe 10 is provided with a flow rate adjusting valve 14, and oxygen gas is supplied from the top blow lance 3 at an arbitrary flow rate. In this way, oxygen gas or nitrogen gas can be blown in as a transfer gas at an arbitrary flow rate via the dispenser 11. In this case, instead of nitrogen gas, various gases such as Ar gas and carbon dioxide can be used as the carrier gas.

  The top blowing lance 3 is composed of four types of concentric steel pipes (not shown), that is, a quadruple pipe, which are an outer pipe, an intermediate pipe, an inner pipe, and an innermost pipe in order from the outside. CaO-based dephosphorizing agent 17 used as a carrier gas passes through the innermost tube, oxygen gas passes through the gap between the inner tube and the innermost tube, the gap between the outer tube and the intermediate tube, and the inner tube and the inner tube. The gap with the pipe is a cooling water supply / drainage channel. When carrying out the dephosphorization processing method according to the present invention, the top blowing lance 3 does not have to serve as a supply flow path for the CaO-based dephosphorizing agent 17. You may install the lance for supply of the anti-glazing agent 17. FIG. In this case, the upper blow lance 3 does not need to be a quadruple tube, and a plurality of ordinary triple tube lances may be arranged. However, since the equipment arrangement in the upper part of the furnace body 2 becomes complicated, in order to prevent this, it is preferable that the top blowing lance 3 also serves as a supply flow path for the CaO-based dephosphorizing agent 17.

  Using the converter type refining equipment 1 having such a configuration, the dephosphorization treatment according to the present invention is performed on the hot metal 15 as follows.

  First, the hot metal 15 is charged into the furnace body 2. When iron scrap is used, iron scrap is charged into the furnace body 2 before the hot metal 15 is charged. The hot metal 15 used can be processed with any composition, and may be subjected to desulfurization treatment or desiliconization treatment before dephosphorization treatment. The desiliconization process is a process in which iron oxide such as mill scale or oxygen gas is added to the hot metal 15 to mainly remove silicon contained in the hot metal 15. Incidentally, the main chemical components of the hot metal 15 before the dephosphorization treatment are carbon: 3.8 to 5.0% by mass, silicon: 0.6% by mass or less, sulfur: 0.05% by mass or less, phosphorus: 0.00%. It is about 08-0.3 mass%. However, if the amount of slag 16 generated in the furnace body during the dephosphorization process increases, the dephosphorization efficiency decreases. Therefore, in order to increase the dephosphorization efficiency by reducing the amount of slag generated in the furnace body, It is preferable to perform a silicon removal treatment and reduce the silicon concentration of the hot metal 15 to 0.2% by mass or less. Moreover, if the hot metal temperature is in the range of 1250 to 1350 ° C., dephosphorization can be performed without any problem.

  Next, a non-oxidizing gas such as nitrogen gas or a rare gas such as Ar gas is blown into the hot metal 15 from the bottom blowing tuyere 7 as a stirring gas 18, and oxygen gas is directed from the top blowing lance 3 toward the bath surface of the hot metal 15. And the CaO-based dephosphorizing agent 17 is supplied through the top blowing lance 3 toward the spraying surface of the oxygen gas on the hot metal bath surface, that is, toward the hot spot, and the hot metal 15 is removed. Start phosphorus treatment.

In this case, as the CaO-based dephosphorizing agent 17, powdered quicklime (CaO) can be used. Alumina powder or fluorite may be added to the quicklime powder as a hatching accelerator, but in the present invention, the CaO-based dephosphorizing agent 17 is added by spraying on the hot spot of the hot metal bath surface. Even if the powder itself is sufficiently hatched, it can be sufficiently dephosphorized without using a hatching accelerator such as alumina powder or fluorite. In particular, from the viewpoint of protecting the environment by suppressing the amount of fluorine eluted from the slag 16, it is preferable that a fluorine-containing substance such as fluorite is not mixed with the CaO-based dephosphorizing agent 17. However, a substance in which fluorine is inevitably mixed as an impurity component may be used. In addition to quicklime, powders such as limestone (CaCO ₃ ), slaked lime (Ca (OH) ₂ ), and dolomite (CaCO ₃ · MgCO ₃ ) can also be used as the CaO-based dephosphorizing agent 17.

  The hot metal 15 is stirred by the stirring gas 18 blown from the bottom blowing tuyere 7, and the CaO-based dephosphorizing agent 17 sprayed on the hot metal bath surface is melted at a hot spot to form a slag 16. The dephosphorization reaction proceeds.

  During the dephosphorization process, a carbon source 21 derived from biomass and containing an ash content of 9% by mass or less is introduced from the carbon source addition device 20 into the furnace body. Since the carbon source 21 needs to be melted in the hot metal 15 at the start of the carbon source 21, it is not preferable at the final stage of the dephosphorization process. It is preferable to start the introduction of the carbon source 21 before at least half of the time during which oxygen gas is supplied. When the charging is started, it is preferable to continuously charge until a predetermined amount of the carbon source 21 is completely added. However, as described above, “continuously charging” includes not only continuous addition but also the case where the carbon source 21 is charged at a short time interval of about 2 minutes or less. The amount of the carbon source 21 added is adjusted according to the carbon concentration in the hot metal before the dephosphorization treatment, but about 10 kg per ton of hot metal is sufficient. Since it does not carburize more than the saturation concentration of the carbon in the hot metal 15, even if it adds excessively, it will only cause the deterioration of a yield.

If only oxygen gas is used as the oxygen source during the dephosphorization process, the hot metal temperature will rise too high and the dephosphorylation reaction may be hindered. Therefore, if necessary, iron oxide such as mill scale or iron ore can be used as a solid oxygen source. May be added. The ratio between the amount of oxygen gas added and the amount of solid oxygen source added can be appropriately changed according to the silicon concentration, phosphorus concentration, carbon concentration, etc. of the hot metal 15. The amount of CaO-based dephosphorizing agent 17 is changed according to the silicon concentration and phosphorus concentration of the hot metal 15, but the basicity (mass% CaO / mass% SiO ₂ ) of the slag 16 is If it is in the range of 2 or more, a maximum of about 40 kg per ton of hot metal is sufficient. The lance height is not particularly limited, and may be set in consideration of the amount of slag 16 generated.

  As described above, in the hot metal dephosphorization method according to the present invention, the hot metal 15 is dephosphorized by spraying the CaO-based dephosphorization medium solvent 17 toward the oxygen gas spray surface of the hot metal bath surface. Since the carbon source 21 derived from biomass and having an ash content of 9% by mass or less is added to the inside of the furnace body 2 and dispersedly added in the furnace body, the place of dephosphorization reaction and the place of carburization reaction The carbon source 21 derived from biomass and having an ash content of 9% by mass or less is dissolved in the hot metal 15 without inhibiting the dephosphorization reaction and reducing the dephosphorization processing capacity. Since the speed is high, the hot metal 15 can be carburized quickly and efficiently. As a result, the heat margin of the hot metal 15 can be increased, and in the converter decarburization refining in the next process, it becomes possible to reduce the mixture ratio of hot metal and increase the amount of manganese ore added. In addition to energy saving, stabilization of converter decarburization operation is achieved. Further, in the case where a fluorine-containing substance such as fluorite is not mixed with the CaO-based dephosphorizing agent 17, the elution of fluorine from the slag 16 is considered when the slag 16 generated by the dephosphorization process is reused. Therefore, the reuse of the slag 16 can be promoted.

  When a hot metal holding container such as a torpedo car or hot metal ladle is used as the refining container, the oxygen gas from the top blowing lance and the supply of the CaO-based dephosphorizing agent 17 to the hot metal are carried out as described above. The supply of the carbon source 21 to the hot metal is added on the hot metal bath surface using a charging chute, or is blown into the hot metal using a blowing lance. In other cases, the dephosphorization treatment may be performed in accordance with the above.

  The hot metal discharged from the blast furnace is desiliconized in a hot metal ladle, then desulfurized using a mechanical stirring device, and then charged into a converter type refining facility having a capacity of 250 tons shown in FIG. Then, the hot metal dephosphorization treatment according to the present invention was carried out (example of the present invention).

In the dephosphorization treatment, oxygen gas is blown from the top blowing lance onto the hot metal bath surface, and at the same time, only quick lime powder is used as a CaO-based dephosphorizing agent, and nitrogen gas is used as the carrier gas, and the hot metal is passed through the top blowing lance. It was carried out by spraying quick lime powder toward the hot spot of the hot water surface. During the dephosphorization treatment, a carbon source was continuously added to the furnace body from a hopper installed above the furnace body. Further, nitrogen gas was blown from the bottom blowing tuyere at a supply rate of 0.07 to 0.12 Nm ³ / (min · t), and the hot metal was stirred. The hot metal temperature before and after the treatment was adjusted to a range of 1280 to 1350 ° C. The amount of hot metal was 225 tons, and the amount of iron scrap was 15 tons.

  As a carbon source derived from biomass and having an ash content of 9% by mass or less, biomass carbon derived from palm coconut shell (PKS) having an ash content of 5.9% by mass (hereinafter referred to as “biomass coal A”) , Biomass charcoal derived from palm palm trunk (hereinafter referred to as “biomass charcoal B”) having an ash content of 8.1% by mass, and palm palm empty fruit bunch having an ash content of 8.8% by mass (EFB) ) Biomass charcoal (hereinafter referred to as “biomass charcoal C”). Further, as a comparative carbon source, coke having an ash content of 11.2% by mass and graphite having an ash content of 18.0% by mass were also used. The amount of carbon source added was fixed at 6.5 kg / t for all operations. Furthermore, dephosphorization treatment without adding a carbon source was also carried out.

In Table 1, the operation conditions and operation results in the present inventions 1 to 9 and Comparative Examples 1 to 9 are shown. Comparative Examples 1 to 3 are operations in which no carbon source is added. The “dephosphorization oxygen basic unit” in Table 1 is obtained by subtracting the oxygen content necessary for the production of SiO ₂ from the total oxygen basic unit, and the “treatment time” (= dephosphorization treatment time) is: This is a period during which oxygen gas is supplied from the top blowing lance, and “addition start time” is expressed as an elapsed time after the supply of oxygen gas from the top blowing lance is started. Further, the “decarburization amount” is defined by the following equation (4).
Decarburization amount (mass%) = (carbon concentration in hot metal before treatment (mass%)) x [molten metal blending amount (t) / (molten metal blending amount (t) + iron scrap blending amount (t))]-(treatment Carbon concentration in hot metal after (mass%)) (4)

  FIG. 2 shows the correlation between the amount of decarburization and the amount of dephosphorization in Invention Examples 1 to 9 and Comparative Examples 1 to 3. As shown in FIG. 2, Examples 1 to 9 of the present invention have an effect of reducing the amount of decarburization by adding a carbon source while the amount of dephosphorization is substantially the same as that of Comparative Examples 1 to 3. It was. Further, in Invention Examples 1 to 9, the dephosphorization time and the oxygen gas basic unit are substantially the same as those of Comparative Examples 1 to 3 in which no carbon source is added, and the amount of oxygen supplied by the addition of the carbon source is There were no operational problems such as increase and extended processing time.

  Moreover, in FIG. 3, the correlation with the ash content in the carbon source in this invention examples 1-9 and comparative examples 4-9 and the amount of decarburization is shown. In addition, in order to eliminate the influence on the decarburization amount by the carbon source addition start timing, the ratio of the carbon source addition start time to the dephosphorization processing time was made constant at 0.12. In Invention Examples 1 to 9 using a biomass-derived carbon source having an ash content of 9% by mass or less, the dissolution rate of the carbon source into the molten iron is fast, and the amount burned by oxygen gas is the same. It was found that the amount of decarburization was smaller than that of Comparative Examples 4 to 9 even with the addition amount.

  As described above, in Examples 1 to 9 of the present invention, since the carbon source having a high dissolution rate in the hot metal is used, the dephosphorization reaction site and the carburization reaction site can be separated by the dispersion addition of the carbon source. Combined with this, hot metal can be carburized quickly and efficiently without hindering the dephosphorization reaction, and powdered quick lime is directly projected to the hot spot to add conventional lump quick lime. It was confirmed that the dephosphorization treatment can be performed efficiently with a quick lime basic unit smaller than that of the method.

  In order to investigate the influence of the carbon source addition start time on the decarburization amount in the present invention, the carbon source addition start time was changed in the dephosphorization treatment of the present invention in the converter type refining equipment used in Example 1. And the effect on decarburization amount was investigated. As the carbon source, biomass coal A having an ash content of 5.9% by mass used in Example 1 was used.

  Table 2 shows the operation conditions and operation results of the present invention 10-16. FIG. 4 shows the relationship between the value obtained by dividing the carbon source addition start time by the dephosphorization time and the amount of decarburization.

  As is clear from FIG. 4, when the carbon source addition start time was in the latter half of the dephosphorization processing time, the effect of reducing the decarburization amount was reduced. This is because a certain amount of time is required for the carbon source to dissolve in the hot metal, and even if it is added at the end of the dephosphorization process, the carbon source does not completely melt in the hot metal but only remains in the slag. This is because the yield decreased. That is, it was confirmed that it is preferable to start the carbon source input by the first half of the dephosphorization treatment.

DESCRIPTION OF SYMBOLS 1 Converter type refining equipment 2 Furnace main body 3 Top blowing lance 4 Iron skin 5 Refractory 6 Outlet 7 Bottom blowing tuyere 8 Gas introduction pipe 9 Oxygen gas piping 10 Nitrogen gas piping 11 Dispenser 12 Flow rate adjustment valve 13 Flow rate adjustment valve 14 Flow control valve 15 Hot metal 16 Slag 17 CaO-based dephosphorizing additive 18 Stirring gas 19 Antioxidant transfer pipe 20 Carbon source addition device 21 Carbon source

Claims (4)

Oxygen gas is blown through the top blowing lance toward the hot metal bath surface contained in the refining vessel, and the hot metal bath is sprayed with a CaO-based dephosphorization medium solvent to remove the hot metal. When the phosphorous treatment is carried out, the biomass-derived biomass charcoal derived from the palm and having an ash content of 9% by mass or less, the biomass charcoal derived from the palm palm empty fruit bunch, and the biomass charcoal derived from the palm palm trunk are contained in the refining vessel. A method for dephosphorizing hot metal, which comprises adding one or more carbon sources.   The refining vessel is a converter-type refining vessel, and the carbon source is collided with an upper blowing lance standing upright in the converter-type refining vessel, and the carbon source is dispersed in the converter-type refining vessel by this collision. The hot metal dephosphorization method according to claim 1, wherein the hot metal dephosphorization treatment is performed. 3. The hot metal dephosphorization method according to claim 1 or 2, wherein the carbon source is continuously added. The addition start timing to the carbon source in the refining vessel, characterized by up to the time of the expiration of 1/2 the processing time required for dephosphorization any one of claims 1 to 3 The method for dephosphorizing hot metal as described in 1.

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