TWI704231B - Converter facility - Google Patents

Abstract

The present invention provides a converter facility including: a first electrode disposed such that a tip end is immersed in a slag formed on a molten iron alloy bath in a converter; a second electrode disposed so as to contact the molten iron alloy bath or the slag; a power supply device for supplying a DC current to the first electrode and the second electrode via the slag; and a control unit that controls the DC current not exceeding the preset maximum output current.

Description

Converter equipment

Invention field The present invention relates to a converter equipment used to obtain molten slag with reduced metallic iron content and its inconsistency more stable than before when refining molten iron alloys in converter equipment.

Background of the invention Free CaO is contained in molten slag (hereinafter also referred to as "converter slag") generated during converter refining of molten iron alloys such as molten pig iron (hereinafter also referred to as "melt milling"), which will cause hydration reaction and expand , So the volume stability is low.

In addition, although it is also related to the treatment method, the molten slag usually contains about 1-40% by mass of iron oxide, which makes the appearance black. If it is used for concrete aggregates, the appearance may be inconsistent. sense.

Therefore, the use of slag is limited to low-level applications such as road foundation improvement materials or lower road base materials, and it is difficult to use it in upper road base materials, concrete aggregates, stone materials, etc.

Therefore, conventionally, the molten slag is discharged from the converter to the reaction vessel, and a reforming material such as coal ash is added to the molten converter slag in the vessel to reduce free CaO. More advanced applications, such as upper road base material or concrete aggregates.

In addition, in the converter slag, about tens of mass% of granular iron is contained in a suspended state as metallic iron. There are the following problems: because there is carbon in the suspended granular iron, and during the modification of the molten slag, the carbon of the granular iron reacts with the iron oxide in the molten slag or the oxygen used for stirring, and thus the CO gas bubbles (bubbles) are generated in the slag and bring various adverse effects. In addition, due to the presence of granular iron, when the slag is reused, uneven distribution of the granular iron or oxidative expansion of the granular iron may cause inconsistencies in the strength of the slag. In addition, the granular iron in the slag is the main reason for the loss of yield when the converter is focused, and the lower the content, the better. If the amount of granular iron in the slag is inconsistent, it will be difficult to directly and instantly measure the amount of granular iron in the slag. Therefore, when the molten slag is processed and the granular iron is recovered from the cooled slag, the processing on the side of repeated processing has to be selected, which leads to deterioration in efficiency. In addition, the blistering during the melt reforming treatment also caused inconsistencies in the treatment time, making it difficult to perform stable treatment.

In addition, for example, Patent Document 1 discloses a method of performing a slag reforming treatment after the granular iron in the molten slag taken out from the converter is settled in a reaction vessel. However, even in this case, if there is an inconsistency in the amount of granular iron in the slag, there will still be inconsistencies in the settling time, making it difficult to perform stable processing.

In this way, since in the past, after the converter slag is discharged into the reaction vessel, the treatment of reducing the metallic iron in the slag is performed in the reaction vessel. Therefore, if the amount of granular iron in the slag is inconsistent, there may Inconsistency in the slag treatment time occurs.

However, in recent years, the following attempts have been made: As reported in Non-Patent Document 1, in converter refining, an oxygen supply lance is used as an electrode on one side, and a voltage is applied between the electrode on the other side of the furnace bottom , And measure the change of current, voltage and resistance value in the middle of blowing, so as to obtain the distance between the tip of the spray gun and the molten metal bath surface, the thickness of the slag layer and other information.

However, the impact on the properties of molten slag caused by electrification has not been specifically reviewed. Prior art literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2006-199984 Non-patent literature

Non-Patent Document 1: Current distribution characteristics in a converter bath when a potential is applied to molten steel, C.I. Semikin, V.F. Polyakov, E.V. Semkina, 2003

Summary of the invention Problems to be solved by the invention The purpose of the present invention is to obtain a slag with a smaller metal iron content and its inconsistency in the molten slag when refining molten iron alloy in a converter, and to reduce the content of the molten slag in the subsequent slag modification treatment. The treatment of iron is simplified, and the problem is to provide a converter equipment that can stably obtain slag with less inconsistency in the metal iron content in the slag. Means to solve the problem

The gist of the present invention is as follows.

(1) The first aspect of the present invention is a converter equipment, including: a first electrode arranged so that its tip is immersed in the slag generated above the molten iron alloy bath in the converter; The ferroalloy bath or the aforementioned molten slag is connected; a power supply device, through the aforementioned molten slag, supplies a direct current to the aforementioned first electrode and the aforementioned second electrode; and a control device, which controls the aforementioned direct current not to exceed the preset maximum output current .

(2) In the converter equipment described in (1) above, the power supply device may supply direct current to the first electrode and the second electrode through the slag and the molten iron alloy bath.

(3) In the converter equipment described in (1) or (2) above, it may also be that the first electrode is a hollow top-blowing oxygen supply lance, and the second electrode is provided on the bottom or belly of the converter .

(4) In the converter equipment described in any one of (1) to (3) above, the control device may also control the supply amount of the direct current to be constant.

(5) In the converter equipment described in any one of (1) to (4) above, it may also be that the control device has a resistance value between the first electrode and the second electrode after blowing starts When the resistance value is set in advance or less, it is controlled to cut off the supply of the aforementioned direct current. (6) In the converter equipment described in any one of (1) to (5) above, the response speed of the power supply device may be 0.1 second or less. (7) In the converter equipment described in any one of (1) to (6) above, the control device may be controlled so that the direct current becomes 50 A or more. Invention effect

According to the converter equipment of the present invention, the energization of the metal bath can be performed stably and safely, and the amount of granular iron contained in the slag and its inconsistency can be reduced. In addition, by reducing the inconsistency of the amount of granular iron, it becomes possible to stably carry out the recovery process of the metallic iron by the magnetic screening in the subsequent step, and it is possible to stably obtain a slag with a reduced metallic iron content than before. As a result, the yield of iron in the converter can be improved, and the efficiency of the slag reforming treatment can be improved.

The form used to implement the invention The inventors of the present invention conducted a review of the method for reducing the content of granular iron in the molten slag and its inconsistency when refining molten iron alloys with a converter, and focused on energizing the slag bath and the metal bath. In addition, it has been found that when a specific amount of electric charge is applied during energization, the amount of granular iron contained in the slag and its inconsistency are reduced.

Hereinafter, the present invention based on the above-mentioned knowledge will be explained with reference to the drawings. Furthermore, in this manual, unless otherwise specified, "%" means "mass%", and "current" means "direct current". In addition, the current control is configured to be controlled by a control device not shown.

In converter refining, melt milling sent from a blast furnace is poured into the converter, and a slag material containing CaO as the main component is added to perform blowing for the purpose of desiliconization and/or dephosphorization, and refined dephosphorization Blowing for the purpose of decarburization and temperature adjustment.

Fig. 1 is a side view showing a converter facility 1 of this embodiment. In this converter facility 1, the first electrode 21 is installed so that the tip is immersed in the slag 11 generated above the molten iron alloy bath (hereinafter also referred to as "iron bath 12"). Specifically, the first electrode 21 is embedded in the hearth and arranged so that the tip end becomes the height position between the upper surface of the slag 11 and the upper surface of the iron bath 12. The second electrode 22 is arranged to be in contact with the iron bath 12.

By arranging the electrodes in this manner and connecting them to the power supply device 40 provided outside the converter, the slag 11, the iron bath 12, the first electrode 21, and the second electrode 22 can form a circuit. Therefore, it becomes possible to apply a voltage between the electrodes and supply current to the slag 11 and the iron bath 12 during refining. The first electrode 21 can also be used as a hollow top-blowing oxygen spray gun 31 as shown in FIG. 3.

There are usually 3 methods for blowing kneading in a converter: 1) The conventional blowing method of desiliconization, dephosphorization and decarburization; 2) A blowing method that separates the blowing for the purpose of desiliconization and/or dephosphorization, and the blowing for the purpose of precise dephosphorization and decarburization and temperature adjustment; and 3) A blowing method that separates blowing for the purpose of dephosphorization and blowing for the purpose of precise dephosphorization and decarburization and temperature adjustment after desiliconization in other steps.

In the case of 2) and 3) above, it is advisable to set the time of energization to be any of the blowing for the purpose of desiliconization and/or dephosphorization and the blowing for the purpose of fine dephosphorization and decarburization and temperature adjustment. One blow or two blows. In each of the above 1) ~ 3) blowing, especially when applied at the end of blowing, a greater effect can be obtained.

In Figures 2A and 2B, in the 400-ton converter, the first electrode 21 connected to the side of the molten slag 11 is arranged on the hearth, and the second electrode 21 connected to the side of the iron bath 12 The electrode 22 is arranged at the bottom of the furnace, and a current of 350A or less is supplied between the electrodes during the period of 24 seconds immediately before the cessation of blowing during dephosphorization blowing, and 24 seconds before the cessation of blowing during decarburization blowing When a current of 350A or less is supplied between the electrodes for blowing during the period (ON) and when there is no current between the electrodes (OFF), the relationship between the average current value, the amount of granular iron, and their inconsistencies during the period is displayed. The results shown in Fig. 2A and Fig. 2B are the results of the following blowing method: 3) After desiliconization in other steps, blowing for the purpose of dephosphorization, and refined dephosphorization and decarburization, and The temperature adjustment is for the purpose of blowing and separating.

In each case, the slag after blowing was taken out for 5 feeds and sampled by the reduction method, and the total amount of granular iron and the amount of inconsistency were investigated.

Figure 2A shows the effect of the average current value on the concentration of metallic iron in the molten slag after dephosphorization in the converter. Figure 2B shows the same effect on the concentration of metallic iron in the slag after decarburization. . In both cases, the higher the current value, the lower the iron content, and the disparity in iron content gradually decreases.

When the contents (mass %) of the granular iron contained in the slag shown in FIGS. 2A and 2B are statistically summarized, they become as shown in Table 1 and Table 2 respectively. As shown in Table 1 and Table 2, it can be seen that compared with the case where the current value is OFF, the higher the current value, the average iron content, sample standard deviation, and relative error gradually decrease. It can be seen that the reduction effect is particularly significant when the current value is 50A or more.

Here, the sample standard deviation is the square root of the dispersion value obtained by the sum of the squares of the distance between the value of each sample and the average. Also, the relative error is the value obtained by dividing the standard deviation by the average value. It can be seen from Table 1 and Table 2 that when the current value is set to 50A or more, not only the sample standard deviation but also the relative error is greatly reduced. Therefore, the power supply device 40 preferably controls the current so that the current value becomes 50A or more.

[Table 1] Current value Off (OFF) >50A 100±50A 200±50A 300±50A Average iron content (%) 19.0 18.5 11.0 7.5 2.9 Sample standard deviation 11.3 10.8 5.4 3.7 1.4 Relative error 59 58 49 50 48

[Table 2] Current value Off (OFF) >50A 100±50A 200±50A 300±50A Average iron content (%) 3.3 3.1 1.9 1.3 0.7 Sample standard deviation 2.4 2.2 0.9 0.6 0.3 Relative error 73 72 48 48 46

Usually, the slag after the reforming process is crushed, and the metal iron is recovered by magnetic screening. The results shown in Table 1 and Table 2 above are the following results: by supplying electric current to the slag 11, in addition to the reduction in the content of metallic iron itself, the inconsistency of metallic iron is also reduced, and it shows It has the following major effects: the magnetic screening is stable, and the metallic iron in the slag can be further reduced.

The reason why the above-mentioned effects can be obtained by supplying electric current to the slag 11 in the middle of blowing is not clear, but it can be presumed to be due to the damage to the granular iron remaining in the slag. The energization causes agglomeration and coarsening of the granular iron, which causes the granular iron to settle due to its own weight.

The power supply device 40 is controlled so that the current does not exceed the maximum output current set in advance. For this control, for example, a current detection unit 41 is installed in the middle of the wiring connecting the power supply device 40 and the electrodes, and a signal from the current detection unit 41 is input to the control device 42 to detect the magnitude of the current or the resistance between the electrodes, and The output of the power supply device 40 is controlled in accordance with the magnitude of the detected current.

Specifically, since the resistance value in the converter fluctuates very sharply, instead of performing thyristor control, it is more desirable for the power supply device to perform transistor control. In addition, in the structure of the equipment, it is necessary to consider the range and path through which the current can flow, and to match the part where the allowable energization amount (current) is the smallest, to install the following mechanism: when the output current value exceeds the allowable energization amount Off.

As the first electrode 21, an electrode made of carbon-containing bricks such as MgO-C bricks may be arranged on the furnace sill of the converter. When the bricks in contact with the electrode bricks also contain carbon and the like and there is no significant difference in resistance value, it is desirable to arrange insulating bricks and the like around the electrode bricks. In addition, regarding the conductors connected to the electrode bricks to the outside of the furnace, it is desirable to reduce the resistance as long as they are within the allowable range of equipment configuration or economic restrictions. For example, the area of the joint surface between the copper conductor and the brick is reduced. Enlarging, shortening the distance from the brick working surface to the tip of the copper conductor, etc.

For the second electrode 22, carbon-containing bricks or the like can be used. The second electrode 22 is preferably arranged on the bottom or the hearth of the converter equipment 1. When the second electrode 22 is provided on the furnace web, the height of the second electrode 22' as shown in FIG. 4 may be set to be in contact with the molten iron alloy bath or the slag 11. Furthermore, in the case of the example shown in FIG. 4, the power supply device 40 is configured to supply a direct current to the first electrode 21 and the second electrode 22 without passing through the iron bath 12 and only passing through the slag 11.

When arranging the first electrode 21 on the hearth, the first electrode 21 should be set on the basis of the static liquid level of the iron bath 12 conceived from the volume of the converter, and set above 200mm~4000mm, and preferably on Above 200~400mm. If it is set lower than the 200mm upper position based on the static liquid level, the frequency of the short circuit will increase due to the vibration of the metal surface and the frequency of current flowing in the slag will decrease, thereby reducing the effect. If the position is higher than the 4000mm upper position based on the static liquid level, the frequency of the electrode contacting the slag part will decrease, and the effect will also be weakened.

The power supply device 40 has a mechanism that cuts off the supply of current when the current value flowing between the first electrode 21 and the second electrode 22 exceeds the maximum allowable current value set in advance.

In this equipment, when a current exceeding the maximum allowable current value flows, it is determined that there is no proper current flowing in the slag because, for example, the current passes through the attached bare metal. In addition, when a current exceeding the maximum allowable current flows, this current will not be recorded as the current used for converter processing. With this, when the slag is sent to the post-processing step after refining in the converter, the value of the current flowing only in the slag can be used as information of the slag in the converter to be transmitted in addition to the characteristics of the slag. In the post-processing step, it is only necessary to perform processing according to the current value information, so that excessive post-processing is unnecessary and the post-processing step is stabilized.

In addition, the method of determining the maximum allowable current can be determined by experimenting to distinguish between the current flowing in the slag or the current flowing in other systems, namely the furnace wall of the converter or the bare metal attached to the refractory. OK. The maximum allowable current is also a fixed value.

One of the methods for determining whether it is the current flowing in the slag is the method of using the resistance value. If the circuit resistance between the first electrode, the power supply and the second electrode is grasped in advance by calculation or actual measurement, the resistance of the entire circuit can be easily measured from the state of being energized during blowing This resistance value is subtracted to obtain the resistance value between the electrodes.

Generally, the resistance value when passing through the slag is larger than the resistance value of bare metal, etc., and it can be observed as a significant difference. The specific resistance value varies with the thickness of the slag, the position of the electrode, and the composition or properties of the slag (liquid phase ratio or metal or bubble content), so it can be grasped by measuring in advance.

Furthermore, the range of the current value flowing in the slag in the converter may be determined from the inconsistency of the current value flowing in the slag, and the upper limit may be determined as the maximum allowable current. In this case, for example, the following current value can be set as the maximum allowable current: a value obtained by adding a value of three times the difference of the current value to the average current value flowing in the slag.

In addition, the following mechanism can also be provided: the current is cut off after the maximum allowable current is detected, and the current is switched on again after a set time, for example, 30 seconds or more.

As shown in FIG. 3, a top-blowing oxygen supply spray gun 31 can also be used as the first electrode 21. In addition, in the case of using the top-blowing oxygen spray gun 31 as the first electrode 21, the tip can also be set up and down, and it can be set up and down according to the current flowing between the electrodes and control the flow to The magnitude of the current in the slag.

In the case of using the top-blowing oxygen supply spray gun 31 as the first electrode 21, insulation measures must be applied to the mechanism supporting the spray gun and the oxygen or cooling water supply and discharge system. In addition, if there is a mechanism for sealing the spray gun and the spray gun insertion hole, such as a seal cone, insulation measures around this part may also be necessary. In addition, in the case of using a top-blowing oxygen supply lance 31 as the first electrode 21, it is preferable that at least the tip portion is made of copper from the viewpoint of wear resistance.

When the top-blowing oxygen lance 31 is used as the first electrode 21, compared with the case of using the electrode of the furnace web, it becomes more stable to allow current to flow to the slag.

In the case of using the electrode of the furnace web, it is considered that the furnace wall deposits become the main energizing path and the current does not flow through the entire slag. On the other hand, when the top-blowing oxygen supply lance 31 is used as the first electrode 21, in addition to the state of the slag, the relative position of the lance and the slag may significantly change the resistance in the furnace. Therefore, the position of the spray gun must be as low as possible. It is expected that the spray gun can be in contact with the slag. However, since the conductivity of the atmosphere in the furnace itself is also increased due to iron vapor or the like during blowing, it is not necessary to be in a state where the spray gun is in contact with the slag.

With the degree of freedom of the spray gun position, it is desirable to control the spray gun position in accordance with the current value or the resistance value as described above. When the spray gun position is low, the heat load from the ignition point or the steel bath is high, and the scattered bare metal has a strong tendency to adhere to the spray gun, which may cause the spray gun life to be reduced or work obstacles.

The position of the spray gun can be determined based on operating experience. If the position of the spray gun is set higher, the contact area with the slag will decrease, or the resistance value will increase due to the gas layer (the space above the slag containing fine dust and steam), which is relative to the same voltage condition The current value becomes lower. Therefore, it is desirable to lower the spray gun to below the position where the lowest current value corresponding to the empirically obtainable effect can be ensured, and there is no doubt about the reduction of the spray gun life or the operation hindrance.

In the case where the top-blowing oxygen supply lance 31 is used as the first electrode, the maximum allowable current can be set similarly to the case where the first electrode is arranged in the furnace web.

In addition, the power supply device may also have a function of controlling so that the supply value of current does not exceed a fixed value (hereinafter also referred to as "constant current control"). It is more preferable if the power supply device 40 has a constant current control function that changes the voltage in response to the resistance in the furnace and sets the current supply amount to be fixed. By controlling the current to be almost constant during blowing, the amount of granular iron in the slag can be controlled to be less inconsistent.

In the constant current control, the upper limit of the current can be set to be distinguishable from the current flowing in the slag and the current flowing in systems other than the slag. In addition, for example, the upper limit may be set to the inconsistency (standard deviation value) of the set current value + the current. In addition, the lower limit may be set to 0A to avoid applying excessive voltage when the resistance value is high due to the properties of the slag.

The set current value when performing constant current control can also be set by the relationship between the inconsistency of the amount of granular iron in the slag determined by experiments and the inconsistency of the amount of granular iron allowed in the post-processing step. For example, in Figures 2A and 2B, since the sample standard deviation when 200A current flows in the dephosphorization step is 3.7%, and this value is also an allowable value in the post-processing step, the current value can also be set Set to 200A.

Preferably, the power supply device 40 includes a mechanism that cuts off the supply of current when the resistance value between the first electrode 21 and the second electrode 22 is equal to or less than a preset resistance value. The resistance value is obtained by inputting the signal from the current detection element 41 to the control device 42. In addition, the following mechanism may also be provided: if the obtained resistance value is less than the preset resistance value for the time set in advance from the start of blowing, the output of the power supply device 40 is stopped and cut off The supply of electric current.

Since the resistance value of the slag is known in advance, it can be estimated that the resistance value is lower than that means that the current does not flow in the slag, but flows in a system other than the slag. Therefore, by obtaining the resistance value, it becomes possible to recognize whether the current flows into the slag.

In addition, the determination of the above-mentioned maximum allowable current or resistance value is as described below, which also contributes to the stabilization of the device. In other words, immediately after the start of blowing, it is the dissolution or foaming of additives, etc., that allow current to flow stably in the slag 11, which has not yet been completed. Therefore, when the first electrode 21 suddenly comes into contact with the slag 11, there is a possibility that the resistance drops sharply and the current value rises sharply. In this case, some current values may damage the equipment due to heat. By having a mechanism that cuts off the supply of current, it is possible to cut off the current in this case to avoid accidents.

In addition, even in cases where stray current flows outside the converter due to some abnormalities, the supply of current can be cut off, so that the equipment can be operated safely.

It is expected that the response speed of the power supply device 40 is 0.1 second or less. As mentioned above, the resistance value in the furnace greatly changes from a substantially insulating state to below the micro-ohm that is assumed to be a short circuit caused by bare metal, and its state changes in seconds.

For example, there is not a sufficient amount of slag immediately after the start of blowing, and the ambient gas in the furnace is also in a state of low electrical conductivity, and is substantially in a nearly insulated state. On the other hand, in the case where a desired energization path through the slag is assumed, it is conceivable that although it depends on the state of the slag, a resistance of about 100 mΩ is formed.

That is, in the case where rapid bubbling of slag has occurred, the resistance value may be instantaneously reduced from the insulated state to 100 mΩ. When the response speed of the output control is slow, the circuit may be cut off even though the current value rises and flows through a sound path when it cannot follow the huge change in the resistance value.

Because even if the maximum output current has been set in a sound range and the smallest resistance value is assumed, the resistance value will still vary from 1 to 2 digits depending on the state of the slag or the presence or absence of intermediary in the gas phase. Therefore, the same is true for the rapid change from the state of high resistance value to the state of low resistance value.

Therefore, in order to ensure stable power supply, the response speed of the power supply device must follow these state changes. According to the facts discovered by the inventors of the present invention through experiments, the resistance value in the furnace may fluctuate at intervals of about 0.1 seconds. Therefore, it is expected that the response speed of the power supply is 0.1 second or less. At this time, the response speed means that the change from the maximum current to the minimum current or the opposite change is completed within that time.

In addition, this equipment can also be equipped with a bottom blowing port 50 composed of perforated bricks and multiple pipes or manifolds at the bottom of the furnace, and blow gas into the iron bath 12 through the bottom of the furnace during refining. Bath 12 is stirred. Although there may be only one bottom blowing port 50, it is better to provide a plurality of them. Fig. 1 is an example showing a case where bottom blowing ports 50 are provided at two locations.

In the present invention, the composition of the slag to be processed is not limited to a specific composition. For example, it can be a composition with alkalinity: 0.5 or more and iron oxide concentration: 5% or more.

In the case of slag composed of alkalinity: 0.5 or more and iron oxide concentration: 5% or more, the resistance value of the slag is easy to change depending on the composition, and there may be a sudden current value when the slag is connected to the electrode. Therefore, the method of using the current control mechanism of the present invention is effective.

Although the composition of the molten iron alloy to be processed is not limited to a specific composition, if it is applied to the case of processing molten pig iron whose silicon concentration has been set to 0.25% or less, the effect will increase. This is because although the amount of slag is usually less when the silicon concentration is low, the amount of granular iron produced is determined by the amount of energy (mainly top blowing) or decarburization in the furnace. When the amount of slag is small, the concentration of granular iron in the slag will be relatively increased. Therefore, when this treatment is performed, a significant effect can be obtained by using the device of the present invention.

In addition, it is also appropriate to use the equipment of the present invention when treating molten iron in an area of 2.5% or more at the carbon concentration at the end of refining. This is because most of the refining in such areas is carried out at a lower alkalinity and ends at a low temperature, so the viscosity of the slag is high, and the amount of granular iron contained in the slag is large. reason.

In addition, the present invention can be applied to any of the following cases: the case where the desiliconization and dephosphorization steps are carried out in other refining vessels, the case where the respective steps are carried out in separate converters, the case where the two steps are carried out in the same converter Happening.

Although the energization is performed in the latter half of the blowing, it is effective in guiding the energization in a state where the density of the granular iron in the slag has increased. For this reason, it is advisable to supply electric current during a period of 1 minute retrospectively from the stop of oxygen supply, that is, the period from 1 minute before the stop of oxygen supply to the stop of oxygen supply.

As described above, according to the converter equipment of the present invention, the energization of the metal bath can be performed stably and safely, the amount of granular iron contained in the slag can be reduced, and the reduced metal iron can be obtained more stably than before. The content of slag.

In addition, although an example of the embodiment of the present invention has been described, the present invention is not limited to the description of the above-mentioned embodiment of the invention. As long as the description does not deviate from the scope of the patent application and can be easily conceived by those with ordinary knowledge in the technical field, various modifications are of course also included in the present invention.

(Example) Hereinafter, a more specific example is given to explain an example of the refining method using the converter equipment of the present invention. In addition, the following example is an average result of an embodiment or a reference example under multiple feeding conditions of about 20 feedings.

(Example 1) The 300t-scale top-bottom blown converter was renovated, and MgO-C bricks were installed at the bottom of the furnace, and MgO-C bricks were installed on both sides of the trunnion side at a position 2000 mm away from the furnace bottom as the upper electrode. . The inner diameter of the furnace is 6000mm, and the depth of molten iron is 1700mm. The height of the spray gun is set so that the distance from the liquid level to the tip of the spray gun becomes 3000 mm, and blowing is performed. There are 2 oxygen blowing ports at the bottom of the furnace.

The energization starts simultaneously with the start of oxygen supply, and the energization ends simultaneously with the end of oxygen supply. The power supply uses a structure with a mechanism that cuts off the current when a current exceeding the maximum allowable current flows. Set the maximum allowable current to 500A on this device. In addition, when the resistance value of the slag measured in advance has been assumed, the voltage of the power supply is set so that a current of 250 A flows through the slag.

The melt milling composition is adjusted to C: 3.8 to 3.9%, Si: 0.01%, P: 0.02%, and Mn: 0.01%, the end composition is adjusted to C: 0.04%, and the temperature is about 1650°C.

At the beginning of blowing, there is current flowing in about 40% of the feed. The aforementioned current can be regarded as the current affected by the bare metal attached to the furnace wall. Since the current value has exceeded 500A, the power supply was cut off. After that, repeat the following method: turn on the power again every 30 seconds, and turn off the power when there is more than 500A circulating. Since all of these about 40% of the feed will be in a state of almost no current flow from 2 minutes to 2.5 minutes from the start of blowing, it will remain in that state directly afterwards.

The bare metal adhering to the furnace wall is presumed to be the bare metal that was directly attached and left undissolved by mixing with the slag in the previous feed, or the bare metal attached during the melt milling of the feed . If you consider the situation that is eliminated within a few minutes after the start of blowing, the possibility of melt milling is higher. Furthermore, during this period, the current over 500A observed after the power is turned on again is not included in the average current value used to verify the effect.

At the beginning of blowing, if the current presumed to be affected by the bare metal is not flowing, the circuit will continue to be energized without cutting off the circuit from the beginning (the current is not observed immediately after the start). The current value gradually rises from the area where the resistance value in the furnace is high and the current cannot be detected at the initial stage, and reaches 220-270A after 3 to 3.5 minutes after the start of blowing. After that, the current value maintains the aforementioned current level even if there is a slight change, and the current circulates almost stably and ends during the entire blowing for 14 to 14.5 minutes, except for the interruption of the power supply during temperature measurement and sampling.

After each round of blowing, the molten slag was discharged almost in its entirety, and after cooling, after coarse pulverization, the content of metallic iron in each charge was evaluated.

The average current value in blowing is about 200A, and it is in the range of plus or minus 20A. The average amount of granular iron in the slag is 7.0%, indicating that the standard deviation of the sample that is not consistent is 3.4%.

In this way, since the inconsistency in the amount of granular iron can be quantified, from the next time on, the current value flowing in the converter is notified as the information indicating the properties of the slag. Since this information is used to set the processing time in the post-processing step, stable processing can be performed.

(Example 2) The 300t-scale top-bottom blowing converter was renovated, and MgO-C bricks were installed at the bottom of the furnace. In addition, the power supply was connected to the spray gun on the furnace wall as the upper electrode. The inner diameter of the furnace is 6000mm, and the depth of molten iron is 1700mm. The height of the spray gun is set so that the distance from the liquid level to the tip of the spray gun becomes 3000 mm, and blowing is performed. There are 2 oxygen blowing ports at the bottom of the furnace.

The energization starts simultaneously with the start of oxygen supply, and the energization ends simultaneously with the end of oxygen supply. The power supply uses a structure with a mechanism that cuts off the current when a current exceeding the maximum allowable current flows. Set the maximum allowable current to 500A on this device. In addition, when the resistance value of the slag measured in advance has been assumed, the voltage of the power supply is set so that a current of 250 A flows through the slag.

The melt milling composition is adjusted to C: 3.8 to 3.9%, Si: 0.01%, P: 0.02%, and Mn: 0.01%, the end composition is adjusted to C: 0.04%, and the temperature is about 1650°C.

As in Example 1, at the start of blowing, only one feed has current flowing, and the aforementioned current can be regarded as the current affected by the bare metal attached to the insulating part of the spray gun hole. Since the current value has exceeded 500A, the power supply was cut off. After that, when the power was turned on again after 30 seconds, the current hardly flowed, so the state was maintained as it was.

Since the bare metal was deposited in the previous feed or just after the blowing of this feed, and short-circuited the insulation part, it can be presumed that it was dissolved and removed by the heat from the furnace or the Joule heat when 500A was energized. Of bare metal. The current over 500A observed in this feed is not included in the average current value displayed later.

The other feeds did not observe the aforementioned current, so they continued to be energized without cutting off the circuit. However, the current was not observed in the early stage of blowing (~2 minutes or so). In all the feeds, the current value gradually rises to 250A about 3 to 3.5 minutes after the start of blowing. After about 2.5 to 3 minutes, the current value gradually decreased after about 250A was almost steadily circulated. However, about 9 minutes after the start of blowing, the current rose again, and a current of about 150 to 200A was observed. This current circulates almost stably until the end of blowing for 14 to 14.5 minutes, except for the interruption of power supply during temperature measurement and sampling. Turn off the power before the end of blowing.

The average current value in blowing is about 100A, and is in the range of plus or minus 10A, the average amount of granular iron in the slag is 6.2%, and the standard deviation of the sample indicating inconsistency is 2.3%.

As in Example 1, the value of the average value of the current normally flowing (in this case, about 100 A) is used as the information of the slag to notify the post-processing step. Since this information is used to set the processing time in the post-processing step, stable processing can be performed.

(Reference example) The 300t-scale top-bottom blown converter was renovated, and MgO-C bricks were installed at the bottom of the furnace, and MgO-C bricks were installed on both sides of the trunnion side at a position 2000 mm away from the furnace bottom as the upper electrode. . The inner diameter of the furnace is 6000mm, and the depth of molten iron is 1700mm. The height of the spray gun is set so that the distance from the liquid level to the tip of the spray gun becomes 3000 mm, and blowing is performed. There are 2 oxygen blowing ports at the bottom of the furnace.

The energization starts simultaneously with the start of oxygen supply, and the energization ends simultaneously with the end of oxygen supply. The power supply uses a structure with a mechanism that cuts off the current when a current exceeding the maximum allowable current flows. Set the maximum allowable current to 500A on this device. In addition, considering the resistance value of the slag, it was set to flow a current of 200 A in the converter.

The melt milling composition is adjusted to C: 3.8 to 3.9%, Si: 0.01%, P: 0.02%, and Mn: 0.01%, the end composition is adjusted to C: 0.04%, and the temperature is about 1650°C. The energization starts simultaneously with the start of oxygen supply, and the energization ends simultaneously with the end of oxygen supply.

In addition, when the resistance value of the slag measured in advance has been assumed, the voltage of the power supply is set so that a current of 250 A flows through the slag. The power supply uses a configuration that does not have the following mechanism: When a current exceeding the maximum allowable current flows, the current is cut off.

As in Example 1, there is current flowing in 45% of the feed. The aforementioned current can be regarded as the current affected by the bare metal attached to the furnace wall at the beginning of blowing. Although the current value will exceed 500A, it still continues to be energized and blowing without cutting off the power supply.

In these feeds, the current decreased when 2 minutes passed after the start of blowing, and a current of about 250 A was shown at 3 minutes. From the change in resistance value, it can be inferred that the bare metal is energized in the first 2 minutes, and then the slag is energized. The average current value after that is set to include the current value exceeding 500A during this period.

In the remaining 55% of the feed, although the aforementioned current is not observed, the current value will gradually rise to 250A at 3 to 3.5 minutes after the start of blowing. Although in all subsequent feeds, the current value gradually decreased after about 250A was almost steadily circulated for about 2.5~3 minutes, but further about 9 minutes after the start of blowing, the current increased again, and 150~200A was observed About the current. This current circulates almost stably until the end of blowing for 14 to 14.5 minutes, except for the interruption of power supply during temperature measurement and sampling. Turn off the power before the end of blowing.

The average current value during blowing is more than 300 A for the initial energization, and approximately 250 A for the feed where no energization is observed at the initial stage. The average amount of granular iron in the slag is 7.2%, indicating that the standard deviation of the inconsistent samples is 3.3%. However, when comparing the feed with an average current value of more than 300 A and the feed with an average current value of 250 A, there is no difference in effect.

On the other hand, because the former feed material exceeding 300A directly informs the post-processing step of the current average value, the processing speed in the magnetic separation process is reduced to correspond to it, resulting in the deterioration of the recovery efficiency of bare metal.

In addition, the initial energization of more than 500A continued for more than 2 minutes. When the inside of the furnace was observed after tapping of the feed, it was confirmed that the wear of the electrode to the lower furnace wall brick was abnormally increased. In the case of evaluating the average loss rate in the interval of dozens of feedings including this feeding, it is clear that an increase equivalent to about 10% is formed. It can be considered that the wear of the refractory is extremely advanced due to the Joule heat generated when a large current passes through the bare metal.

(Example 3) The 300t-scale top-bottom blowing converter was remodeled, and MgO-C bricks were installed at the bottom of the furnace, and MgO-C bricks were installed on the furnace wall at a position 2000 mm from the furnace bottom as the upper electrode. The inner diameter of the furnace is 6000mm, and the depth of molten iron is 1700mm. The height of the spray gun is set so that the distance from the liquid level to the tip of the spray gun becomes 3000 mm, and blowing is performed. There are 2 oxygen blowing ports at the bottom of the furnace.

The energization starts simultaneously with the start of oxygen supply, and the energization ends simultaneously with the end of oxygen supply. The power supply uses a structure with a constant current control mechanism. The response speed is 0.5 seconds. The constant current value is set to 300A, and its allowable range is set to +50A~300A.

The melt milling composition is adjusted to C: 3.8 to 3.9%, Si: 0.01%, P: 0.02%, and Mn: 0.01%, the end composition is adjusted to C: 0.04%, and the temperature is about 1650°C.

At the beginning of blowing, there is current flowing in about 40% of the feed. The aforementioned current can be regarded as the current affected by the bare metal attached to the furnace wall. Since the current value has exceeded 350A, the power supply was cut off. After that, repeat the following method: turn on the power again every 30 seconds, and turn off the power when there is more than 500A circulating. Since all of these about 40% of the feed will be in a state where there is almost no current flow from 2 to 2.5 minutes from the start of blowing, it will remain in that state directly afterwards.

Furthermore, during this period, the current over 500A observed after the power is turned on again is not included in the average current value used to verify the effect.

At the beginning of blowing, if the current presumed to be affected by the bare metal is not flowing, the circuit will continue to be energized without cutting off the circuit from the beginning (the current is not observed immediately after the start). Since the lower limit of the constant current control is set to 0A even when the current is not observed, the current value maintained in the original state gradually rises from the area where the resistance value in the furnace is high and the current cannot be detected at the beginning, and it is blowing It will reach 300A after 3~3.5 minutes after the start of the exercise. After that, the current value is almost unchanged by the output control of the power supply. Except for the interruption of the power supply during temperature measurement and sampling, a current of about 300A almost stably flows through the entire blowing for 14 to 14.5 minutes and ends.

The average current value in blowing is about 240A, and it is in the range of plus or minus 20A. The average amount of granular iron in the slag is 2.6%, indicating that the standard deviation of the sample inconsistent is 1.4%.

In this way, since the inconsistency in the amount of granular iron can be quantified, from the next time on, the current value flowing in the converter is notified as the information indicating the properties of the slag. Since this information is used to set the processing time in the post-processing step, stable processing can be performed.

(Example 4) The 300t-scale top-bottom blowing converter was remodeled, and MgO-C bricks were installed at the bottom of the furnace, and MgO-C bricks were installed on the furnace wall at a position 2000 mm from the furnace bottom as the upper electrode. The inner diameter of the furnace is 6000mm, and the depth of molten iron is 1700mm. The height of the spray gun is set so that the distance from the liquid level to the tip of the spray gun becomes 3000 mm, and blowing is performed. There are 2 oxygen blowing ports at the bottom of the furnace.

The energization starts simultaneously with the start of oxygen supply, and the energization ends simultaneously with the end of oxygen supply. For the power supply, the power supply used in Example 3 is used, and a calculation mechanism for calculating the resistance value of the circuit is added. The upper limit of the resistance value is set to 1Ω, and the lower limit of the resistance value is set to 0.05Ω. In addition, a current of 300 A is controlled to flow within the range of the upper and lower limits of the set resistance value.

Furthermore, when the calculated resistance value exceeds the upper and lower limits of the set resistance value, a voltage as low as 5V is applied to the current flowing in the circuit. In the range of the resistance value from 0.05Ω to 1Ω, a fixed current can flow.

The melt milling composition is adjusted to C: 3.8 to 3.9%, Si: 0.01%, P: 0.02%, and Mn: 0.01%, the end composition is adjusted to C: 0.04%, and the temperature is about 1650°C.

Regarding the resistance value, at the beginning of blowing, a decrease in the resistance value can be observed. The aforementioned resistance value can be regarded as the resistance value affected by the bare metal attached to the furnace wall. Since the resistance value is below 0.05Ω, 300A is not circulating. After continuing to observe the resistance value, the state below 0.05Ω disappears, but because the state continues to exceed 1Ω immediately thereafter, the current of 300A does not flow.

In addition, since the resistance value becomes 1Ω or less and 0.05Ω or more after 3 to 3.5 minutes after the start of blowing, the current value is set to 300A. End the blowing for 14~14.5 minutes, and end the power on before the end of the blowing.

In these blowing, the average current value is about 240A, and is in the range of plus or minus 20A, the average amount of granular iron in the slag is 2.7%, indicating that the sample standard deviation of inconsistency is 1.3%.

In this way, since the inconsistency in the amount of granular iron can be quantified, from the next time on, the current value flowing in the converter is notified as the information indicating the properties of the slag. Since this information is used to set the processing time in the post-processing step, stable processing can be performed.

(Example 5) Under the same conditions as in Example 4, the power supply was changed to a device with a response speed of 1 millisecond (msec). It can be observed that the blowing and energizing conditions are the same as in Example 4.

However, due to the increase in response speed, the current value hardly changes, and the average current value is about 240A, which is within the range of plus or minus 5A. In addition, the average range of this current value is more affected by the energization start time (the time when the furnace resistance is within the allowable range) than it is affected by the fluctuation of the power supply output during energization.

The average amount of granular iron in the slag is 2.4%, which means that the standard deviation of the inconsistent samples is 1.2%.

In this way, since the inconsistency in the amount of granular iron can be quantified, from the next time on, the current value flowing in the converter is notified as the information indicating the properties of the slag. Since this information is used to set the processing time in the post-processing step, stable processing can be performed.

By using the converter equipment of the present invention, current can be stably flowed in the slag and the slag/iron bath interface. Thereby, the amount of granular iron in the slag can be reduced, and the post-treatment of the slag can be performed stably. Industrial availability

According to the converter equipment of the present invention, since the energization can be carried out stably and safely, the amount of granular iron contained in the slag can be reduced, and the slag with a reduced metal iron content can be obtained more stably than before. Improve the iron yield and improve the efficiency of the post-treatment of molten slag, that is, the reforming treatment. As a result, it is possible to obtain slag that can be used not only for road foundation improvement materials or lower road base materials, but also for upper road base materials, concrete aggregates, stone raw materials, etc., so it is very likely to be industrially used. .

1: Converter equipment 11: slag 12: Iron bath 21: First electrode 22, 22’: second electrode 31: Top blowing oxygen supply spray gun 40: power supply unit 41: Current detection component 42: control device 50: bottom blow

Fig. 1 is a schematic diagram showing an example of the converter equipment of the present invention. Fig. 2A is a graph showing the relationship between the average current value during the melt milling dephosphorization period and the content of granular iron in the slag. Fig. 2B is a graph showing the relationship between the average current value during the decarburization period and the content of granular iron in the slag. Fig. 3 is a schematic diagram showing another example of the converter equipment of the present invention. Fig. 4 is a schematic diagram showing another example of the converter equipment of the present invention.

1: Converter equipment

11: slag

12: Iron bath

21: First electrode

22: second electrode

31: Top blowing oxygen supply spray gun

40: power supply unit

41: Current detection component

42: control device

50: bottom blow

Claims (7)

A converter equipment, characterized by comprising: a first electrode arranged to be immersed in the slag generated above the molten iron alloy bath in the converter; and a second electrode arranged to be in contact with the molten iron alloy bath or the slag A power supply device, through the slag, supplies a direct current to the first electrode and the second electrode; and a control device that controls the direct current not to exceed a preset maximum output current, and the first electrode is hollow Top blowing oxygen spray gun. The converter device of claim 1, wherein the power supply device supplies a direct current to the first electrode and the second electrode through the molten slag and the molten iron alloy bath. Such as the converter equipment of claim 1 or 2, wherein the aforementioned second electrode is provided on the bottom or hearth of the converter. The converter equipment of claim 1 or 2, wherein the control device controls the supply amount of the direct current to be fixed. Such as the converter equipment of claim 1 or 2, wherein the control device controls the direct current when the resistance value between the first electrode and the second electrode is less than the resistance value set in advance after blowing starts The current supply is cut off. Such as the converter equipment of claim 1 or 2, wherein the response speed of the aforementioned power supply device is less than 0.1 second. Such as the converter equipment of claim 1 or 2, wherein the aforementioned control device controls the aforementioned direct current to become 50A or more.

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