JP7147550B2 - Slag foaming suppression method and converter refining method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a slag foaming suppression method and a converter refining method.

Hot metal produced in a blast furnace in the steel manufacturing process has a C concentration of 4 to 5% by mass and a P concentration of about 0.1% by mass. It is difficult to use as Therefore, dephosphorization and decarburization are performed in the refining process, and various components are adjusted to produce steel that satisfies the required quality. In this dephosphorization/decarburization treatment, oxygen gas and slag containing FeO are used to oxidize and remove C and P in the hot metal. Phosphorus and decarburization reactions proceed in parallel.

At present, the main refining process, including the pretreatment process, is the converter system, which has good productivity and reaction efficiency. The method of operation is to charge blast furnace hot metal into a converter and perform desiliconization and dephosphorization blowing. is discharged from the furnace throat, the converter is returned to a vertical position, and then decarburization blowing is performed (hereinafter referred to as a continuous treatment method). As another operation method, after charging blast furnace hot metal into a converter and performing desiliconization blowing, the blowing is temporarily stopped and the converter is tilted, and part of the desiliconization slag is discharged from the furnace mouth. After the dephosphorization blowing, the molten iron is once discharged from the converter and separated from the dephosphorization slag, and only the molten iron is separated from the dephosphorization slag. Patent Literature 1 discloses a method (hereinafter referred to as a separation treatment method) in which decarburization blowing is performed by recharging into the furnace. The former is an operation mode using one converter, and is a system in which slag is discharged from the furnace throat between desiliconization/dephosphorization blowing and decarburization blowing. The latter is an operation mode using two converters, one of which is used for desiliconization and dephosphorization blowing, and in the converter, slag discharged from the furnace throat is desiliconized and desiliconized. This method is performed in the middle of the phosphorus blowing process. Both have in common that the volume of slag is increased by utilizing the slag foaming phenomenon that occurs during blowing in order to efficiently discharge slag from the furnace throat.

Forming of converter slag occurs when C in hot metal reacts with oxygen gas or FeO in slag during blowing to generate a large number of CO bubbles, which stay in the slag. A reaction in which CO bubbles are generated is represented by the formula (A).
C + FeO = CO (g) + Fe (A)

In both the continuous treatment method and the separation treatment method, the slag formed in the furnace is discharged from the furnace mouth and stored in the slag pan installed below the converter. As the amount of slag discharged to the slag pan increases, the amount of SiO ₂ and P ₂ O ₅ remaining in the furnace can be reduced, ensuring the slag basicity (CaO/SiO ₂ ) necessary for dephosphorization. It is possible to reduce the amount of refining materials such as quicklime that are put in for the purpose of Therefore, it is desirable to discharge a large amount of slag in a short period of time. requires effort. It is possible to avoid overflowing by slowing down the slag discharge rate or temporarily interrupting slag discharge, but this reduces productivity, so substances that suppress slag foaming are put into the slag pan. be.

Slag overflow from the refining vessel due to forming is a phenomenon that hinders productivity not only in slag ladle but also in torpedo trucks, hot metal ladle, and converter. For this reason, various foaming suppression methods have been tried so far. Conventional foaming suppression methods can be broadly classified into two. The first is a method of suppressing the generation of air bubbles. For example, Patent Document 2 discloses an anti-foaming agent that suppresses the generation of CO gas by absorbing heat during thermal decomposition by adding a carbonate such as raw dolomite. ing. The other is a method of destroying (breaking) the air bubbles remaining in the slag. For example, Patent Literature 3 discloses a foaming tranquilizer formed mainly from pulp waste slag. This foaming tranquilizer rapidly generates gas by combustion or thermal decomposition reaction in the slag, and its volume expansion energy causes the bubbles to break and the slag to shrink.

In addition, in Patent Documents 4 to 6, focusing on the fact that water quickly vaporizes at high temperature, is easy to obtain, and is inexpensive, mist-like or jet-like water is sprayed against molten slag, and slag A method of suppressing foaming by breaking or solidifying the surface is disclosed.

As a sedative method by both suppressing CO gas generation and promoting bubble breakage, Patent Document 7 discloses a foaming inhibitor containing Al and S. It is said that this foaming suppression mechanism suppresses the generation of bubbles by reducing FeO in the slag with Al, and reduces the interfacial tension between the slag and the metal by S, making it difficult to stably maintain the bubbles.

Non-Patent Document 2 also discloses the effect of S on the slag forming phenomenon. According to this, when the S concentration of the slag increases, the generation speed of CO bubbles decreases, making it difficult to generate CO bubbles. It is said that the foam breaks in a short time due to the

JP 2013-167015 A Japanese Patent Application Laid-Open No. 2003-213314 JP-A-54-32116 JP-A-5-195040 JP-A-8-325619 Japanese Patent No. 5888445 Japanese Patent Application Laid-Open No. 2000-328122

Tetsu to Hagane, 87 (2001) No. 1, pp. 21-28 Tetsu to Hagane, 1992, No. 11, pp. 1682-1689

In the above-described continuous treatment method and separation treatment method, the slag is continuously discharged from the throat of the converter and vigorously stirred at the dropping position, so that C of pig iron grains suspended in the slag and FeO of the slag A large amount of CO bubbles are continuously generated by the reaction, and rapidly foam even in the slag pan. Since the volume of the slag pan is generally much smaller than that of the converter, foaming must be effectively suppressed in order to discharge a large amount of slag from the converter into the slag pan in a short period of time.

To address this problem, the method of Patent Document 2 is such that oxides (e.g., CaO, MgO) after generating CO ₂ gas by thermal decomposition tend to remain undissolved in the slag. May cause volumetric expansion. Next, in the method of Patent Document 3, the molded body may be crushed by its own weight in the charging hopper and become powdery, and even if it is charged, it will remain on the slag surface and will not settle or rise up. Sufficient effect is difficult to obtain. If the input amount is increased to compensate for this, the amount of ash in the pulp waste slag that is blown up as dust increases when gas is generated by the reaction of combustion or thermal decomposition, and there is a risk of worsening the working environment.

The methods of Patent Documents 4 to 6, which spray water, do not cause residual slag, change in shape, or deterioration of the working environment, but the relationship between the water spray speed and the slag discharge speed is not disclosed. It is difficult to obtain a sufficient effect on slag which is discharged continuously and foams violently.

In the method of Patent Document 7, the temperature of the slag rises due to the reaction heat generated when Al reduces FeO in the slag. There is a risk that the rate of occurrence of will increase and inhibit the foaming suppression effect. Moreover, if part of the S contained in the charged sedative material remains undissolved, there is a risk that harmful H ₂ S gas will be generated when the discharged slag is cooled by spraying water.

The present invention has been made in view of such problems, and is capable of efficiently suppressing foaming when continuously discharging slag from the furnace throat into a slag pan, leaving undissolved slag, and deteriorating the working environment. It is also an object of the present invention to provide a method that does not generate toxic gas. The foaming suppression method of the present invention includes a converter refining method (continuous processing method) in which desiliconization/dephosphorization blowing, slag and decarburization blowing are continuously performed in one converter, or two converters. It can be used in a converter refining method (separation treatment method) in which desiliconization blowing, slag and dephosphorization blowing are performed in one of the two.

ｗ_ore：硫化鉱物の排滓前投入量（ｋｇ）
Ｗ_slag-1：排滓開始から１分間の最大スラグ排出量（ｋｇ）
(％Ｓ)_ore：硫化鉱物のＳ濃度（質量％）
Ｗ_slag：スラグ排出量（ｋｇ）
Ｖ_water：水噴流の吹き付け速度（ｋｇ／分）
Ｖ_slag：スラグの排出速度（ｋｇ／分）
［２］前記硫化鉱物の粒度は、粒径２０ｍｍ以下が８０質量％以上であることを特徴とする、前記［１］に記載のスラグのフォーミング抑制方法。 A method for suppressing slag foaming according to the present invention that meets the above object is as follows.
[1] A method for suppressing slag forming by charging a sulfide mineral containing 20 to 55% by mass of S into a slag pan installed below a converter, wherein the slag is discharged from the throat of the converter. Then, an amount of sulfide mineral that satisfies the formula (1) is put into the slag pot, and the time when the amount of slag discharged satisfies the conditions of the formula (2) is used as a starting point, and the formula (3) A method for suppressing slag foaming, characterized by spraying a water jet at a speed that satisfies the range in a range within a radius of 1 m from the falling center of the slag stream in the slag pan.

w _ore : Amount of sulfide mineral input before slag (kg)
W _slag-1 : Maximum amount of slag discharged in one minute from the start of slag discharge (kg)
(% S) _ore : S concentration of sulfide mineral (% by mass)
W _slag : Slag discharge amount (kg)
V _water : Spraying speed of water jet (kg/min)
V _slag : Slag discharge rate (kg/min)
[2] The method for suppressing slag foaming according to [1], wherein the grain size of the sulfide mineral is 80% by mass or more with a grain size of 20 mm or less.

Further, the converter refining method according to the present invention is as follows.
[3] After charging molten iron into one converter and performing desiliconization and dephosphorization blowing, the converter is tilted with the molten iron remaining in the furnace to discharge slag from the furnace mouth, and In a refining method in which decarburization blowing is performed after the furnace is returned to a vertical position, the method for suppressing slag foaming described in [1] or [2] is used when slag is discharged after dephosphorization blowing. Converter refining method.
[4] After hot metal is charged into one of the two converters and desiliconization is performed, the converter is tilted with the hot metal remaining in the furnace to discharge slag from the furnace mouth, and the converter is In a refining method in which dephosphorization blowing is performed after returning to a vertical state , hot metal is discharged from the converter, and only the hot metal is charged into the other converter again for decarburization blowing , desiliconization A converter refining method characterized by using the slag foaming suppression method according to the above [1] or [2] when discharging slag after blowing.

According to the present invention, a sulfide mineral containing a high concentration of S is put into the slag pan before slag discharge, and after the start of slag discharge, the slag S concentration in the former slag pan is 0.1 to 0. Forming can be efficiently suppressed by spraying a water jet at an appropriate speed corresponding to the slag discharge speed from the converter within a period of .4%, and a large amount of slag can be discharged.

Figure showing the change in slag height over time in a small reactor experiment Diagram showing the relationship between slag S concentration and maximum forming height in small reactor experiments Diagram showing the relationship between slag S concentration and maximum CO gas generation rate in small reactor experiments Figure showing the relationship between the slag S concentration and the average bubble diameter in the small reactor experiment Diagram showing changes over time in slag height in a slag pot in an actual machine test Diagram showing slag S concentration change in slag in actual machine test A diagram showing the effect of water jet spraying in an actual machine test Figure calculated by heat balance analysis of slag temperature change in water jet spraying The figure which shows an example of embodiment of this invention

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. In dephosphorization blowing in a converter, oxygen jets are blown onto the hot metal surface at high speed to oxidize P in the hot metal and remove it as P ₂ O ₅ into slag. In parallel with this, Si in the hot metal is also oxidized and migrates to the slag as SiO ₂ . Also, C in the hot metal reacts with oxygen gas or FeO in the slag to generate CO bubbles, some of which stay in the slag to cause foaming.

After the slag forms moderately, the slag is discharged from the furnace mouth into the slag pan installed below the converter, but foaming also occurs in the slag pan. This is because part of the hot metal is torn off by the oxygen jet during blowing and suspended as iron granules in the slag, and the carbon (C) contained in the iron granules is converted into FeO in the slag in the slag ladle. This is because CO bubbles are generated by reacting with

The kinetic energy of the falling slag causes strong agitation in the slag pan, generating a large amount of CO bubbles and violently forming the slag. Therefore, it is necessary to prevent the slag from overflowing by introducing a substance that has a foaming suppression effect.

Ｈ₀：銑鉄投入前のスラグ高さ（ｍｍ）
Ｈ_max：銑鉄投入後の最大スラグ高さ（ｍｍ） The inventors believe that in order to efficiently suppress foaming, it is necessary to simultaneously suppress the generation of bubbles and promote the breakage of bubbles. We paid attention to the fact that it is supposed to have both effects of coarsening the bubble diameter. That is, it was thought that if the slag S concentration was increased by adding an S-containing substance, the gas generation rate would decrease and the gas dissipation rate would increase, and foaming could be efficiently suppressed by the effects of both. Therefore, small furnace experiments were conducted to verify the influence of the S concentration of slag on the forming behavior under the conditions of composition and temperature assumed for the slag discharged from the throat of the above-described continuous treatment method and separation treatment method. Specifically, 100 g of slag was melted at 1350° C. in an iron crucible, and iron sulfide was added to adjust the S concentration. Pig iron was put into this slag from above, and an iron bar was immersed in the slag at regular time intervals. Then, the change in the slag adhesion height of the iron bar over time was measured, and the maximum forming height was calculated by the formula (4) to evaluate the forming suppressing effect.

H ₀ : Slag height before charging pig iron (mm)
H _max : Maximum slag height after charging pig iron (mm)

Fig. 1 shows the change in slag adhesion height over time. In the case of no iron sulfide (S=0.001%), the slag was largely formed, but when the slag S concentration was increased by adding iron sulfide, the forming became difficult. FIG. 2 shows the relationship between the S concentration of slag and the maximum foaming height. The maximum foaming height decreased as the S concentration increased. From the results of FIG. 2, it can be said that if the slag S concentration is 0.1% by mass or more, the forming can be greatly suppressed, and if it is 0.4% by mass or more, the height of the forming will almost completely decrease.

In this experiment, the rate of CO gas generation was measured with a flow meter. In addition, arbitrarily selecting 20 bubbles of the slag adhering to the iron bar and measuring the diameter, the average value of the bubble diameter increased as the S concentration of the slag increased, as shown in FIG. From these results, it was found that by increasing the slag S concentration, the generation rate of CO bubbles decreased and the diameter of the bubbles increased (promotion of bubble breakage), thereby suppressing foaming.

In the present invention, a sulfide ore (sulfide mineral) is preferably used as the S source. The reason for this is that the S grade is high, so it can be expected to be effective even with a small amount of input, the density is high, so it can sufficiently penetrate into the slag even if it is input as it is, and since it does not contain organic matter, black smoke is generated due to thermal decomposition. This is because there is an advantage that there is no In particular, in pyrite, pyrrhotite, and mangablende, most of the elements other than S are constituent elements of slag, such as Fe and Mn, and CaO, SiO ₂ , Al, which may be contained as unavoidable impurities. Since ₂ O ₃ and MgO are also constituents of slag, the risk of causing environmental pollution such as elution of heavy metals is extremely low even if they are added to slag.

Next, a suitable composition range of sulfide minerals will be described. In order to quickly dissolve S contained in the sulfide mineral in the slag, it is preferable that the difference between the S concentration of the slag and the S concentration of the sulfide mineral is large, that is, the S concentration of the sulfide mineral is high. From this point of view, the lower limit of the S concentration of sulfide minerals is 20% by mass. This is because if the content is less than 20% by mass, the S contained in the sulfide mineral is difficult to quickly dissolve in the slag, and the effect of suppressing foaming is reduced. On the other hand, when the S concentration exceeds 55% by mass, simple S is present in the sulfide mineral. Since elemental S has a low boiling point and evaporates easily, it is difficult to dissolve in the slag. In addition, the evaporated S may react with moisture in the air to generate toxic H ₂ S, which is not preferable in terms of working environment. Therefore, in the present invention, the S concentration of sulfide minerals is set to 20 to 55% by mass.

The total concentration of CaO, SiO ₂ , Al ₂ O ₃ and MgO, which are inevitable impurities contained in the sulfide mineral, is preferably 30% by mass or less. This is because sulfide minerals with high concentrations of these elements have a relatively low S concentration and tend to have a small foaming suppressing effect. In particular, SiO ₂ and Al ₂ O ₃ have the effect of increasing the viscosity of the slag, and MgO has the effect of increasing the melting point of the slag. Therefore, the total concentration of these components contained in the sulfide mineral is preferably 30% by mass or less, more preferably 15% by mass or less.

The water content in the sulfide mineral is preferably 10% by mass or less. This is because if the water content is high, H ₂ S gas is likely to be generated after starting the slag discharge.

When a plurality of sulfide minerals are mixed, the weighted average composition of each sulfide mineral should be within the preferred range of the present invention.

The reason why S suppresses foaming is that, as described above, the generation speed of CO bubbles decreases and the diameter of the generated bubbles increases. Based on this mechanism, the inventors came up with the idea of putting sulfide minerals into the slag pan in advance and then discharging the slag, thereby exhibiting the effect of suppressing foaming. At the beginning of the slag discharge, the amount of slag in the slag pot is small, and the slag is strongly agitated and CO bubbles are generated violently. can be effectively suppressed.

In order to verify this idea, we conducted a test on an actual machine. That is, after charging molten iron into the converter and performing desiliconization and dephosphorization blowing, the blowing was temporarily interrupted and the converter was tilted while the molten iron remained in the furnace, and was installed below the furnace body. It was discharged for 5 minutes into a waste pan (inner volume: 70 m ³ ). Sulfide minerals were put into the slag pot before starting the slag removal.

During the slag discharge, the time-dependent change in the amount of slag discharged was measured using a weighing machine attached to a mobile cart holding the slag pot. At the same time, the inside of the slag pot was video-recorded, and the slag height was evaluated from the ratio of the slag surface position to the height from the pot bottom to the pot rim.

The height from the bottom of the slag pan to the edge of the pan is 4.5 m. The slag composition had a basicity (CaO/SiO ₂ ) of 1.0 to 1.2, an iron oxide concentration of 20 to 30% by mass, and a temperature of 1,330 to 1,350°C. Pyrite (S concentration: 49%) was used as the charged sulfide mineral.

Fig. 5 shows the results of the actual machine test. The slag discharge speed was set to 2.5 tons per minute. As the amount of sulfide minerals added before slag is increased, the rate of increase in slag height in the slag pot tends to slow down. time has increased. In addition, the slope of the curve increased from the point where the arrow was given in FIG.

FIG. 6 shows changes over time in the slag S concentration calculated from the amount of sulfide mineral input before slag discharge and the amount of slag discharged. In FIG. 5, the growth of forming accelerated at the timing when the slag S concentration became 0.1% or less. That is, at the beginning of the slag discharge, the S concentration of the slag in the slag pot is high, so that foaming is suppressed. In this way, it was found that foaming can be suppressed by adding sulfide minerals before slag is discharged, and the S concentration of the slag at which this effect can be obtained is 0.1% or more, as in the small reactor experiment. .

ｗ_ore：硫化鉱物の排滓前投入量（ｋｇ）
Ｗ_slag-1：排滓開始から１分間の最大スラグ排出量（ｋｇ）
(％Ｓ)_ore：硫化鉱物のＳ濃度（質量％） The foaming of the slag discharged into the slag pan is most intense during the first minute after the start of slag discharge. Therefore, in the present invention, sulfide minerals are added before slag discharge so that the slag S concentration is 0.1% or more with respect to the maximum amount of slag (W _slag-1 ) that can be discharged in one minute from the start of slag discharge. into the slag pan. However, excessive input of sulfide minerals prior to slag discharge tends to lead to poor dissolution. Therefore, the upper limit of the slag S concentration relative to W _slag-1 is set at 0.4% in order to avoid excessive charging. This is because, as shown in FIG. 2, if the S concentration exceeds 0.4%, the effect of suppressing foaming does not change, so there is no need to increase the S concentration any further. The range of the pre-slag input amount (w _ore ) of the sulfide mineral that satisfies such a condition is expressed by Equation (5) (same as Equation (1) above). The maximum slag discharge amount (W _slag-1 ) for one minute from the start of slag discharge can be determined based on past data. For example, it can be determined as a value obtained by multiplying the average slag discharge amount for one minute from the start of slag discharge by 1.2 times.

w _ore : Amount of sulfide mineral input before slag (kg)
W _slag-1 : Maximum amount of slag discharged in one minute from the start of slag discharge (kg)
(% S) _ore : S concentration of sulfide mineral (% by mass)

As described above, the S concentration of the slag gradually decreases as the slag is discharged, and when the S concentration is less than 0.1% by mass, foaming tends to grow. Therefore, it is conceivable to calculate the S concentration of the slag from the amount of sulfide minerals input before slag discharge and the amount of slag discharged, and add additional sulfide minerals so that the S concentration of the slag can be maintained at 0.1% by mass or more. Since the agitation of the slag becomes weaker as the slag is discharged, some of the sulfide minerals that have been added may remain _undissolved . There is a risk that S will be eluted when the water is removed, causing environmental pollution.

Therefore, the inventors have found that a substance that has the effect of suppressing or calming foaming and that does not leave an unreacted portion even if it is put into the slag is added to the slag before the S concentration of the slag becomes less than 0.1%. After earnestly considering putting it into the water, I came up with the idea of spraying a water jet. Advantages of the water jet are that it does not require hoppers and cutting equipment that are required for continuous addition of solids, that the spray speed is easy to adjust, and that the entire amount evaporates and does not remain in the slag. We thought that by spraying this water jet onto the falling position of the slag stream, water droplets would be caught in the slag and foaming could be suppressed efficiently, and we also conducted an actual machine test.

ｗ_ore：硫化鉱物の排滓前投入量（ｋｇ）
(％Ｓ)_ore：硫化鉱物のＳ濃度（質量％）
Ｗ_slag：スラグ排出量（ｋｇ） In the actual machine test, sulfide minerals were put into the slag pan before the start of slag discharge, and after the start of slag discharge, the S concentration of the slag was calculated from the amount of sulfide minerals input before slag discharge and the amount of slag discharged, and the value was 0. 0.1 to 0.4% by mass, water jet spraying was started. If the spraying start time is too early, H ₂ S may be generated due to the high slag S concentration. Therefore, the slag S concentration at the start of spraying was set to 0.4% by mass or less. The slag discharge amount at which the water jet starts blowing is expressed by Equation (6).

w _ore : Amount of sulfide mineral input before slag (kg)
(% S) _ore : S concentration of sulfide mineral (% by mass)
W _slag : Slag discharge amount (kg)

Ｖ_water：水噴流の吹き付け速度（ｋｇ／分）
Ｖ_slag：スラグ排出速度（ｋｇ／分） As a result of the actual machine test, as shown in FIG. 7, it was found that a sufficient foaming suppressing effect can be obtained when the ratio of the spraying speed V _water of the water jet to the slag discharge speed V _slag is 0.15 or more. On the other hand, when this ratio exceeded 0.6, it became difficult to obtain the effect of suppressing foaming. That is, expression (7) was obtained as a suitable condition for spraying the water jet.

V _water : Spraying speed of water jet (kg/min)
V _slag : Slag discharge speed (kg/min)

In this actual machine test, when the slag temperature after the slag was measured with a radiation thermometer, as shown in FIG. 7, the higher the V _water /V _slag , the lower the slag temperature. In the heat balance analysis, as shown in FIG. 8, when the slag is cooled by the heat of vaporization of H ₂ O, V _water /V _slag is about 5° C. at 0.15 and about 20° C. at 0.60. On the other hand, when the evaporated H ₂ O is decomposed into H ₂ and O ₂ and the heat of decomposition also contributes to slag cooling, V _water /V _slag is reduced by about 20°C at 0.15 and by about 80°C at 0.60. do. Furthermore, when V _water /V _slag increases to 0.8, the temperature drop due to heat of vaporization and heat of decomposition becomes about 110° C., and the temperature is cooled to 1250° C. or less. When the temperature drops to this level, the surface of the slag tends to solidify and become so-called "skinned". When "skinning" occurs, it becomes difficult to promote the breakage of air bubbles, making it difficult to suppress foaming.

That is, the calming effect of water is not only due to the promotion of bubble breakage due to the volume expansion during evaporation, but also due to the decrease in the slag temperature accompanying the evaporation and decomposition reaction of H ₂ O and the decrease in the generation rate of CO bubbles. I found out. However, if the slag is cooled excessively, the surface of the slag will solidify and bubbles will tend to remain inside the slag. Therefore, there is a suitable range for the ratio of the water jet spray speed to the slag discharge speed.

As for the spraying position of the water jet, the dropping position of the slag stream was suitable. “Falling position” is defined as a range within a radius of 1 m from the center of the dropping of the slag stream. Since the slag is vigorously stirred at this position, the sprayed water jet can be caught in the slag, making it easier to efficiently suppress foaming. A test was also conducted in which a water jet was sprayed on a location away from the falling position of the slag stream, but in this case, a sufficient foaming suppressing effect could not be obtained even under the conditions that satisfied formula (7). It is thought that this is because water is less likely to be involved in areas away from the falling position of the slag flow, and evaporates before the slag cooling effect is sufficiently exhibited. Therefore, it is necessary to spray the water jet onto the falling position of the slag stream.

By carrying out the method of the present invention, it is possible to suppress slag forming in the slag pan when slag is discharged from the throat of the converter, and a large amount of slag can be discharged from the converter without causing slag overflow. In addition, there is no residue of sulfide minerals put into the slag pan before slag is discharged, and there is no deterioration of the working environment due to flying dust or the like, and no generation of toxic gases such as H ₂ S.

The spraying of the water jet does not need to be continued until the end of the slag discharge, and if it can be expected that the slag will not overflow from the slag forming state in the slag pot, it may be interrupted in the middle.

It is preferable to stop adding water after the slag is discharged. If the water jet is continued after the slag is discharged, the surface of the slag tends to become "skinned" gradually. This is because if a water jet is further sprayed in this state, a part of the jet may come into contact with the molten slag inside through the gaps in the skin-covered slag, and the vaporized water may not be diffused, causing a steam explosion.

As for the particle size of the sulfide mineral to be added in the present invention, it is preferable that particles having a particle size of 20 mm or less account for 80% by mass or more. This is because particles of more than 20 mm are difficult to quickly dissolve in slag, and the foaming suppressing effect tends to be small.

An example of an embodiment of the invention is shown in FIG. The molten iron 4 is charged into the converter 1 and blown, and the blowing is temporarily interrupted, and the converter 1 is tilted while the molten iron 4 remains in the furnace, and the molten iron 4 is placed in the slag pan 2 installed below the furnace body. It can be used in a converter refining method that discharges slag. Specifically, after charging molten iron 4 into one converter 1 and performing desiliconization and dephosphorization blowing, the converter 1 is tilted while leaving the molten iron 4 in the furnace to remove slag 5. This is a converter blowing method in which the decarburization blowing is carried out continuously after discharging from the furnace mouth and returning the converter 1 vertically. As another converter blowing method, after desiliconization blowing is performed in one of the two converters, the converter 1 is tilted while the hot metal 4 remains in the furnace to remove the slag 5 from the furnace mouth. This is a converter blowing method in which the dephosphorization blowing is carried out continuously after discharging and returning the converter to a vertical position. In any converter blowing method, the sulfide mineral 6 is put into the slag pan 2 before the slag 5 is discharged from the throat of the converter 1, and the slag discharge amount is the condition of the above formula (2) is satisfied, the water jet 3 is sprayed onto the slag dropping position of the slag pan 2 at a speed that satisfies the range of formula (3). Since these methods are similar in that the forming phenomenon is used to discharge slag from the furnace throat, the use of the present invention can provide that effect.

In addition to the refining methods described above, when it is necessary to suppress foaming at the stage of discharging and flowing out slag from one refining vessel to another refining vessel, the present invention can be used to suppress slag overflow.

Examples of the present invention will be specifically described below based on Tables 1 to 3. 400 tons of hot metal is charged into a converter with an internal volume of 300 m ³ and is blown. Blowing is temporarily interrupted and the converter is tilted while the hot metal remains in the furnace. It was discharged into a pan (height from the bottom to the edge of the pan: 4.5 m, internal volume: 70 m ³ ). Before the start of slag discharge, sulfide minerals were put into the slag pan, and after the start of slag discharge, after a predetermined amount of slag was discharged, water jets were continuously sprayed onto the slag in the slag pan. The inside of the slag pan was observed during the slag discharge, and the slag discharge was terminated when the surface of the slag reached the height of the rim of the slag pan. When the slag surface did not reach the height of the edge of the pot, the slag was discharged after 4 minutes from the start of the slag discharge. In Tables 1 to 3, numerical values outside the scope of the present invention are underlined.

The change in weight was measured with a weighing machine attached to a mobile truck on which the slag pan was installed, and the slag discharge amount (W _slag ) at each time point and the total slag discharge amount (W _slag-T ) after slag discharge was completed were evaluated. The total slag discharge amount (W _slag-T ) increases as the foaming suppression effect is superior.

The amount of slag (total amount of slag discharged) is affected by the slag forming in the slag pan, the weight of slag in the converter and the internal volume of the slag pan. Under the conditions of this embodiment, the continuous treatment method with the results shown in Table 2 produces 12 tons or more of waste, and the separation treatment method with the results shown in Table 3 produces 8 tons or more of good waste.

During the tailing, air was sampled every 30 seconds at 1 m above the slag surface and analyzed for hydrogen sulfide concentration. The slag pan was transported to the slag treatment plant, turned over, and sprinkled with water to cool the slag. Air was sampled 1 m above the slag surface during cooling and analyzed for hydrogen sulfide concentration.

Table 1 shows the component composition of the sulfide mineral in this example. A1 and A2 are pyrite, B1 is manganese sulfide ore, and the composition is within the scope of the present invention. C1 and C2 are comparative examples, and the underlined items are outside the scope of the claims. For C2, a mixture of pyrite and high-purity sulfur was used in order to increase the S concentration on a trial basis.

ｗ_ore：硫化鉱物の排滓前投入量（ｋｇ）
(％Ｓ)_ore：硫化鉱物のＳ濃度（質量％）
Ｗ_slag-1：排滓開始から１分間の最大スラグ排出量（ｋｇ） Here, "Ratio A", "Ratio B", and "Ratio C" are defined as indices for determining whether the embodiment is within the scope of the present invention. First, the "ratio A" is a numerical value obtained from equation (8). If this value is 0.1 to 0.4, the amount of sulfide mineral input before slag discharge satisfies the above formula (1).

w _ore : Amount of sulfide mineral input before slag (kg)
(% S) _ore : S concentration of sulfide mineral (% by mass)
W _slag-1 : Maximum amount of slag discharged in one minute from the start of slag discharge (kg)

Ｗ_slag-w：水噴流吹き付け開始時のスラグ排出量（ｋｇ） Also, the "ratio B" is a numerical value obtained from the equation (9). If this value is 0.1 to 0.4, the above formula (2) is satisfied, and the timing of starting the spraying of the water jet falls within the scope of the present invention.

W _slag-w : Amount of slag discharged at the start of water jet spraying (kg)

Ｖ_water：水噴流の吹き付け速度（ｋｇ）
Ｖ_slag：スラグ排出速度（ｋｇ） Furthermore, the "ratio C" is a numerical value obtained from the equation (10). If this value is 0.15 to 0.60, the above formula (3) is satisfied, and the spraying speed of the water jet is within the scope of the present invention.

V _water : Spraying speed of water jet (kg)
V _slag : Slag discharge speed (kg)

Table 2 shows examples of slag after blowing for desiliconization and dephosphorization in a continuous treatment system. The slag composition had a basicity (CaO/SiO ₂ ) of 1.0 to 1.2, an iron oxide concentration of 20 to 30% by mass, and a temperature of 1,330 to 1,350°C. In addition, the maximum slag discharge amount (W _slag-1 ) for one minute from the start of slag discharge under these conditions was 8000 kg.

Examples 1 to 5 are invention examples, and since the method of adding sulfide minerals and the method of spraying water jets were all within the scope of the present invention, the slag could be discharged for 4 minutes without reaching the pot edge height. , the amount of slag was over 12.0t. The generated H ₂ S concentration was 1 ppm or less both during the slag cooling and during the slag cooling. Regarding the particle size of the sulfide ore, in Example 5, the mass ratio of 20 mm or more was higher than in Example 1, so the dissolution into the slag was delayed, and the amount of slag was lower than in Example 1.

Examples 6-15 are comparative examples.
In Example 6, since no sulfide mineral was added, the slag reached the edge of the pot 0.8 minutes after the start of slag discharge, and the amount of slag remained at 6.0 t. In Example 7, since the water jet was not sprayed, the effect of suppressing foaming decreased from the middle of the slag discharge, and the slag reached the edge of the pot 2.0 minutes after the start of slag discharge, and the amount of slag was reduced to 10.0 t. stayed.
In Example 8, since the S concentration of the sulfide mineral was too small from the range of the present invention, the foaming suppression effect was small, and the slag reached the pot edge height 1.5 minutes after the start of slag discharge, and the slag discharge amount was 9.0 t. stayed in In Example 9, since the S concentration of the sulfide mineral was excessively larger than the range of the present invention, the evaporation of S increased, and H ₂ S was generated in the slag at a maximum of 1.2 ppm.
In Example 10, the amount of sulfide mineral added before slag discharge was too small from the range of the present invention, so the foaming suppression effect was small, and the slag reached the edge of the pot 2.0 minutes after the start of slag discharge, and the amount of slag was reduced. It remained at 9.5 tons.
In Example 11, the start of spraying of the water jet was earlier than the range of the present invention, so 1.3 ppm of H ₂ S was generated at maximum. In Example 12, the start of spraying of the water jet was later than the range of the present invention, so a sufficient foaming suppression effect could not be obtained, and the slag reached the edge of the pot 2.3 minutes after the start of slag discharge, and the amount of slag was 10. .5 tons.
In Example 13, the spraying speed of the water jet relative to the slag discharge speed was too small from the range of the present invention, so the foaming suppression effect was small, and the slag reached the pot edge height 2.2 minutes after the start of slag discharge, and the amount of slag was discharged. remained at 10.5 tons. In Example 14, the spraying speed of the water jet relative to the slag discharge speed was excessively higher than the range of the present invention, so a sufficient slag foaming suppression effect could not be obtained, and although slag overflow did not occur, the slag discharge amount was 11.5 tons. stayed.
In Example 15, the spraying position of the water jet was off the falling position of the slag stream, so the foaming suppression effect was small, and the slag reached the edge of the pot 1.5 minutes after the start of slag discharge, and the slag amount was 9.5. Stayed at 3t.

Table 3 shows examples of slag after desiliconization blowing in the separation treatment method. The slag composition had a basicity (CaO/SiO ₂ ) of 0.6 to 0.8, an iron oxide concentration of 20 to 30% by mass, and a temperature of 1,300 to 1,330°C. In addition, the maximum slag discharge amount (W _slag-1 ) for one minute from the start of slag discharge under these conditions was 5000 kg.

Examples 16 to 20 are invention examples, and since the method of adding sulfide minerals and the method of spraying water jets were all within the scope of the present invention, the slag could be discharged for 4 minutes without reaching the pot edge height. , the amount of slag was over 8.0t. The generated H ₂ S concentration was 1 ppm or less both during the slag cooling and during the slag cooling. In addition, in Example 20, since the mass ratio of 20 mm or more was larger than that in Example 16, the dissolution into the slag was delayed, and the amount of slag was lower than in Example 1.

Examples 21-30 are comparative examples.
In Example 21, since no sulfide mineral was added, the slag reached the edge of the pot 0.8 minutes after the start of slag discharge, and the amount of slag remained at 3.0 t. In Example 22, since the water jet was not sprayed, the foaming suppression effect decreased from the middle of the slag discharge, and the slag reached the edge of the pot 2.0 minutes after the start of slag discharge, and the amount of slag was reduced to 6.0 t. stayed.
In Example 23, since the S concentration of the sulfide mineral was too small from the range of the present invention, the foaming suppression effect was small, and the slag reached the pot edge height 1.5 minutes after the start of slag discharge, and the amount of slag discharge was 5.8 t. stayed in In Example 24, since the S concentration of the sulfide mineral was excessively higher than the range of the present invention, the evaporation of S increased, and H ₂ S was generated in the slag at a maximum of 1.2 ppm.
In Example 25, the amount of sulfide minerals added before slag discharge was too small from the range of the present invention, so the foaming suppression effect was small, and the slag reached the edge of the pot 2.0 minutes after the start of slag discharge, and the amount of slag was reduced. It remained at 6.5t.
In Example 26, the start of spraying of the water jet was earlier than the range of the present invention, so 1.3 ppm of H ₂ S was generated at maximum. In Example 27, the start of water jet spraying was later than the range of the present invention, so a sufficient foaming suppression effect could not be obtained, and the slag reached the pot edge height 2.3 minutes after the start of slag discharge, and the amount of slag was 6. .5 tons.
In Example 28, the spraying speed of the water jet relative to the slag discharge speed was too small from the range of the present invention, so the foaming suppression effect was small, and the slag reached the pot edge height 2.2 minutes after the start of slag discharge, and the amount of slag was discharged. remained at 6.5 tons. In Example 29, the spraying speed of the water jet relative to the slag discharge speed was excessively higher than the range of the present invention, so a sufficient slag foaming suppression effect could not be obtained, and although slag overflow did not occur, the slag discharge amount was 7.5 tons. stayed.
In Example 30, the spraying position of the water jet was off the falling position of the slag stream, so the foaming suppression effect was small, and the slag reached the edge of the pot 1.5 minutes after the start of slag discharge, and the amount of slag was 5.5. Stayed at 5t.

REFERENCE SIGNS LIST 1 converter 2 slag pan 3 water jet 4 hot metal 5 slag 6 sulfide mineral

Claims (4)

A method for suppressing slag forming by charging a sulfide mineral containing 20 to 55% by mass of S into a slag pan installed below a converter, wherein the slag is discharged from the throat of the converter, and the formula An amount of sulfide minerals satisfying (1) is put into the slag pot, and the range of formula (3) is satisfied, starting from the time when the amount of slag discharged satisfies the conditions of formula (2). A method for suppressing slag foaming, characterized in that a water jet is sprayed at a high speed in a range within a radius of 1 m from a falling center of the slag stream in the slag pan.

w _ore : Amount of sulfide mineral input before slag (kg)
W _slag-1 : Maximum amount of slag discharged in one minute from the start of slag discharge (kg)
(% S) _ore : S concentration of sulfide mineral (% by mass)

W _slag : Slag discharge amount (kg)

V _water : Spraying speed of water jet (kg/min)
V _slag : Slag discharge speed (kg/min) 2. The method for suppressing slag foaming according to claim 1, wherein 80% by mass or more of the sulfide mineral has a particle size of 20 mm or less. After hot metal is charged into one converter and desiliconization and dephosphorization are performed, the converter is tilted with the hot metal remaining in the furnace to discharge slag from the throat, and the converter is vertically moved. In a refining method in which decarburization blowing is performed after returning to the normal temperature, the method for suppressing slag foaming according to claim 1 or 2 is used when discharging slag after dephosphorization blowing. Method. After hot metal is charged into one of the two converters and desiliconization is performed, the converter is tilted with the hot metal remaining in the furnace to discharge the slag from the furnace mouth, and the converter is set vertically. In a refining method in which dephosphorization blowing is subsequently performed after returning, hot metal is discharged from the converter and only the hot metal is recharged into the other converter for decarburization blowing, after desiliconization blowing 3. A converter refining method, wherein the method for suppressing slag foaming according to claim 1 or 2 is used when discharging slag.

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