KR101424685B1 - Melting slag injection system applied manufacturing unit and its control method - Google Patents

Abstract

The present invention relates to an injection type slag manufacturing device applied with slag melting system and a method for controlling the same, and the slag melting system includes a supplier for supplying collected slag by given quantity; at least two electrode rods for melting the slag supplied from the supplier by means of arc discharging; a melting furnace for receiving the melted slag falling from the electrode rods and having a fireproofing material formed on the receiving surface thereof; driving means for selectively conducting upward/downward driving and tilting driving for the melting furnace in which the melted slag is contained; water granulating means for injecting cooling water to the melted slag discharged from the melting furnace tilting through the driving means to allow the melted slag to be cooled and granulated; and a controller for controlling the supply of the supplier, the electrical control of the electrode rods for their activation, the driving control of the driving means, and the injection conditions of air pressure or cooling water injected from the water granulating means, or all the injection conditions stated above.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slag injection system,

More particularly, the present invention relates to a slag manufacturing apparatus capable of realizing efficient dissolution of a slag and obtaining slag powder immediately after dissolution, and a slag manufacturing apparatus, And a control method of the manufacturing apparatus.

The steel industry uses a large amount of raw materials and energy due to the nature of its manufacturing process, and it is inevitably generating various kinds of waste / busan resources.

In other words, the steelmaking process produces many kinds of by-products and wastes in a large amount through the connection production system of complex processes such as raw materials, steelmaking, steelmaking, rolling and stainless steel, and slag is the largest by-product.

The basic analysis of the slag is a mixture of acidic and basic oxides, which is the remnant after the metal is extracted from the ore and is also called slag. In steel making, this is called steel slag. To remove metals from ores, it is common practice to remove unnecessary components in the ore by making them soluble compounds and then removing them. In the case of steel making, the addition of limestone with iron ore is caused by the fact that the calcium oxide that is generated in the furnace in the future is low in melting and bonding with silica (SiO 2), which is an unnecessary substance in iron ore, This is because it is intended to be a low mixture, and when it exits the furnace, the molten mixture of this mixture forms a layer on the pig iron. Such a mixture is slag. The most important property is that the melting point should be low, and the weight should be lower than that of the required metal so that it should float up and be separated well. In addition, the slag should have a sufficient amount so that impurities that should not be present in the metal of the metal are dissolved and removed in the slag, and moreover, it is necessary to have a property of dissolving such impurities well. The name of the slag varies depending on which type of furnace is used and the name of the slag is different from the electric furnace slag from the electric furnace, the flat slag from the flat furnace, the blast furnace slag from the blast furnace, There are names such as converter slag, etc., and their properties are also different. In addition, the name of the metal to make is called copper material, steel material. In terms of composition, there are silicic acid and non-silicic acid which contain silicic acid as in the case of steel making, and silicic acid is important in metal smelting. In addition to calcium oxide, basic oxides that are relative to silicic acid in silicic acid include magnesia, zinc oxide, iron oxide, alumina, and manganese oxide.

The steel slag is generated from the blast furnace slag generated in the steelmaking process that produces pig iron from the blast furnace using iron ore, coke, and limestone as raw materials, the converter slag generated in the steelmaking process to manufacture steel from the converter, and the electric furnace using scrap metal as the main material An electric furnace slag, etc.

In the steel industry, energy prices have a very large impact on production costs as well as raw material prices. Therefore, countries around the world are striving for rational energy management in the steel industry. Research and development to recover energy from various processes It is actively proceeding. The energy emitted from the steel industry refers to energy that is not reused in the process among the thermal energy or pressure energy of the product or byproduct of each unit process and the recovery energy of many parts is currently being developed, However, much energy that can still be recovered and recycled is being abandoned.

In the field of energy recovery technology, a representative field that has not yet been developed to the practical stage is the technology for recovering the sensible heat of the blast furnace or converter slag.

When producing 1 ton of pig iron in the blast furnace, about 300 kg of blast furnace slag occurs. Its discharge temperature is about 1,400 ° C or more, and it has an enormous sensible heat of about 374 (solid) to 455 kcal (liquid) per 1 kg of blast furnace slag. However, at present, the reason why the blast furnace slag is slowly cooled and then the blast furnace slag is crushed to be used as an aggregate or the like, or quenched with water, is used as a cement admixture, a cement raw material and a fertilizer A considerable amount of sensible heat (about 374 kcal / kg) contained in the melted blast furnace slag is not actually recycled and is being abandoned.

On the other hand, the present Portland Cement by the Rotary Kiln was invented by Joseph Aspidin in 1824, and after the Second World War, the rapid growth of the national land and economy led to a rapid increase in demand for Portland cement, The manufacturing method has changed to various ways and reached to today.

At first, the dry short kiln with the heat generation facilities was the main force. However, through the wet long kiln and the lepol kiln, it is now the era of the dry pre-heater kiln with low heat consumption and mass production effect. It has been converted into a new suspension preheater (NSP) kiln with an additional Weihaso.

The production of portland cement is roughly divided into three processes: a raw material process, a firing process, and a crushing process. In the raw material process, limestone, clay, silica, and iron oxide raw materials are dried and mixed at an appropriate ratio, finely pulverized in a raw material mill, and mixed uniformly. The following firing process is a process in which a raw material blend is fed to a rotary kiln through a suspension preheater and fired at a high temperature of 1,400 ° C or higher, followed by rapid cooling in a cooler to produce a Portland cement clinker. The pulverizing step is a step of adding a suitable amount of gypsum to the Portland cement clinker as a coagulation retarding agent and finely pulverizing the cement with a cement grinder to produce Portland cement. At this time, in cement factories, about 70% or more of cement manufacturing cost is energy cost, so it is a typical energy type rather than blast furnace.

Thus, research on recycling of slag has been actively carried out all over the world, and it is considered to be a representative example of water-slag slag. The water-chain slag collects and melts the generated slag, and then rapidly cooling the slag through a water-cooling process, thereby processing the slag into small particles and applying it to industry.

As mentioned above, it is applied as a cement admixture, and it is recycled for various industrial materials as well.

However, since the conventional process for producing water-milled slag is very complicated and the cost of the process equipment itself is high, there is a disadvantage that it is not suitable for the slag industry market. In addition, since existing facilities are attracting attention for facilities for mass production, they are suffering from economic difficulties and market activation projects.

KR 10-0424810 KR 10-0823616 KR 10-0748117

Accordingly, it is an object of the present invention to provide a slag manufacturing apparatus that can satisfy both low-cost facilities for water-milled slag processing, miniaturization, ease of introduction, and system efficiency.

In particular, the present invention relates to a slag manufacturing apparatus that can be used to manufacture a water-milled slag, which is a fully automated system from the initial supply of slag to the final stage of the manufacture of water-chain slag, and at the same time, The purpose is to provide.

Further, the slag manufacturing apparatus according to the present invention has a complex function capable of rapidly dissolving input slag and producing water-chain slag in the next step, and is capable of producing slag capable of actively controlling the characteristics of the powder produced according to the physical properties of the slag The purpose is to provide a device.

According to an aspect of the present invention, there is provided a method for producing a slag, comprising: a supply unit for supplying the collected slag in a predetermined amount; at least two or more electrodes for melting the slag supplied from the supply unit through an arc discharge; A driving means for selectively driving the melting furnace, the melting furnace in which the slag melt is accommodated, the upper and lower lifting and driving means, and the tilting driving means And a control means for controlling the supply of the supply portion, the electrical control for operating the electrode, the drive control of the drive means, and the control means for controlling the supply and discharge of the molten slag Air pressure or cooling water or spray conditions including both of them And a control unit.

The feeder may further include a hopper for feeding the slag supplied from the outside in a predetermined amount, and a feed screw for feeding and supplying the slag injected into the hopper.

The slag manufacturing apparatus may further include a heating furnace disposed at an upper side of the electrode and primarily heating slag supplied through the feed screw, wherein the heating furnace constitutes an electric heater in a space to supply The transferred slag is primarily heated and freely falls in the furnace, and is melted by the arc discharge generated in the electrode.

The electrode is characterized in that the two electrodes are arranged side by side facing each other.

The melting furnace is composed of a SUS material and has a structure in which a cooling passage for cooling water-cooled inside the sussage of the double structure is provided and cooling water is supplied by external cooling means and circulated .

In addition, the driving means is structured such that it can support the melting furnace of a predetermined size and is structured so that the connecting point connected to the melting furnace is rotatable, and the melting furnace is heated by the pneumatic or hydraulic type elevating or tilting driving of the driving means. / Downward drive and tilting drive.

The control means includes at least one air nozzle for ejecting air and a cooling water nozzle for ejecting cooling water and is connected to an air supply means for supplying air from outside and a cooling water supply means for supplying cooling water, The control unit controls the air supply unit and the cooling water supply unit to inject air and cooling water.

The control means may further include an angle control means for mechanically controlling an injection angle of the air nozzle and the cooling water nozzle through the control means through the control of the control portion.

The control unit may include a first control unit that controls the screw that is configured to supply the supply unit and an applied power source to which the electrode is applied, and a second control unit that controls the spraying condition of the spraying condition.

The present invention also relates to a method for producing a slag, comprising the steps of supplying a collected slag in a predetermined amount, at least two or more electrode rods for melting the slag supplied through the arc discharge, A driving means for selectively driving a melting furnace, a melting furnace in which the slag melt is accommodated, an upper / lower elevating and lowering driving means, and a tilting driving means, a slag melting material discharged as a melting tilted through the driving means And controlling the supply control of the supply portion, the electrical control for operating the electrode, the air pressure or the cooling water jetted from the water-jetting means, or the jetting condition including both of them Application of slag dissolution system including control part A first step of controlling the tilting angle of the melting furnace to control the tilting angle of the melting furnace by controlling the driving means in a stepwise manner to constitute a degassing slag manufacturing apparatus and to discharge the molten slag melt to the outside through the melting furnace; A second step of primarily controlling air injection and cooling water spraying conditions of the water jetting means, a third step of secondarily controlling a tilting angle of the melting furnace after the first step control, And a fourth step of secondarily controlling the air injection and the cooling water jetting conditions configured in the water-jetting means.

The second and fourth steps may further include controlling an angle between the air nozzle and the cooling water nozzle.

Further, before the first step, there is further included a step of performing tilting after the step of raising and lowering the predetermined height in order to secure the height difference of the molten slag due to the tilting of the melting furnace.

The present invention, which is constructed and operated as described above, can quickly dissolve slag charged by using arc discharge. Therefore, since a dissolving apparatus is constituted by an electric energy source, it is possible to dissolve slag by a simple system There are features that can be achieved.

The present invention is also advantageous in that a water chain slag can be produced in one system with a melting furnace capable of tilting molten slag dissolved in a melting furnace through a melting system without any movement.

In addition, since it is possible to easily produce a slag powder by using a single system as a system for manufacturing a slag and operating freely of a dissolving system, it can greatly contribute to an industrial market and has a very high productivity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of an injection type slag manufacturing apparatus to which a slag dissolution system according to the present invention is applied;
FIG. 2 is a front view of a spray type slag manufacturing apparatus to which the slag dissolving system according to the present invention is applied,
FIG. 3 is a side view of a spray type slag manufacturing apparatus to which the slag dissolving system according to the present invention is applied;
4 is an enlarged view showing a melting furnace of a spray type slag manufacturing apparatus to which the slag dissolving system according to the present invention is applied,
5 is a view showing a water chain operation state of a spray type slag manufacturing apparatus to which a slag dissolving system according to the present invention is applied,
FIG. 6 is a view showing a water-jetting means of the spray type slag manufacturing apparatus according to the present invention. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of an apparatus for manufacturing a spray type slag and a method of controlling the same according to the present invention will be described in detail with reference to the accompanying drawings.

The apparatus for manufacturing a spray type slag to which the slag dissolving system according to the present invention is applied comprises a supply part for supplying the collected slag in a predetermined amount, at least two electrodes for melting the slag supplied from the supply part through an arc discharge, A driving means for receiving a slag melt which is melted and dropped in the electrode rod, a refractory material as a receiving surface, a melting furnace, a melting furnace, and a tilting drive for driving the melting furnace, A water supply means for cooling and melting the molten slag by spraying the molten slag so as to be directed toward the slag molten material discharged as a tilting dissolution; an electric control for operating the electrode, a drive control for the drive means, The air pressure or the cooling water jetted from the Is configured to include a controlling the injection conditions including the control.

The slag manufacturing apparatus and the control method thereof according to the present invention can slag supply, melt and multifunctional (multistage, spiral) processes can be automated in one apparatus, and the apparatus can be easily driven, It is an object of the present invention to provide a monolithic slag powder production apparatus having all the features that are very easy to manufacture slag powder as a whole.

Also, as another feature of the present invention, it is a main feature that the properties of the slag powder can be easily determined by providing a multistage process for the classification of the molten slag.

FIG. 1 is an overall configuration view of a spray type slag manufacturing apparatus to which a slag dissolution system according to the present invention is applied.

The apparatus for manufacturing injection type slag according to the present invention roughly comprises a supply part 100 for supplying collected slag, a plurality of electrode bars 200 for dissolving slag falling from the supply part through an arc discharge, A melting furnace 300 containing the slag melt dissolved by the melting furnace, a driving means 400 for tilting the melting furnace, and a water stranding means 500 for milling the slag melt poured through the tilting of the melting furnace.

The present invention is broadly classified into a slag dissolution system and a water chain system. The automatic control system of the present invention is mainly characterized in that it includes a system for controlling the dissolution system such as the supply unit, the electrode rod, 1 control unit 610 and a second control unit 620 for controlling the shovel means, and the control unit 600 includes an operation panel so that the driver can operate the control panel.

Therefore, the apparatus for manufacturing water-chain slag according to the present invention is largely operated in a two-stage process. In the first stage process, the process of melting the collected slag is executed in the fusing system. In the two-stage process, the shank means and the melting furnace are tilted The water-chain slag manufacturing process is operated.

FIG. 2 is a front view of a spray type slag manufacturing apparatus to which the slag dissolving system according to the present invention is applied, and FIG. 3 is a side view of a spray type slag manufacturing apparatus applying the slag dissolving system according to the present invention.

As shown in FIG. 1, a feed part 100 is formed on the upper side of the apparatus so that the slag can be fed from above. The feed part is composed of a hopper 110 and a screw. When the carried slag is put into the hopper, A certain amount of slag is transferred by a screw to be melted.

At this time, a heating furnace 210 for primarily heating the supplied slag is spatially arranged on the upper side of the apparatus, and a plurality of electric heaters are vertically or horizontally arranged inside the heating furnace to primarily heat the slag do. Accordingly, the slag supplied to the inside of the heating furnace along the screw provided in the supply part is then freely dropped, melted in an arc discharge manner through an electrode rod disposed at the bottom, and then accommodated in the melting furnace.

The electrode rod receives a high voltage from a separate power source and generates high heat to dissolve the slag. As shown in the figure, the electrode rods may be formed so as to face the melting space from the side walls opposed to each other. At this time, the electrode rods formed from the inner wall of the melting furnace may be formed to cross each other. And the electrode rods respectively formed on both side walls may be formed so as to fall away from each other when viewed from the front. As an example of the electrode to which the present invention is applied, a moly material electrode may be provided and a copper (Cu) busbar may be applied to receive a high voltage.

Therefore, the slag falling through the arc discharge generated in the electrode rod 200 positioned on the lower side of the heating furnace described above is dissolved due to the high temperature and falls into the melting furnace located directly below the slag. Here, the main feature of the present invention is that since the slag supplied from the supply unit through the electric heater is heated and melted secondarily in the electrode rod 200, the slag can be easily dissolved in a relatively low capacity (voltage) range, It is possible to improve the durability of the electric device, and the stability of the electric design can be kept higher.

Next, the structure of the melting furnace corresponding to the main constitution of the present invention will be described.

4 is an enlarged view showing a melting furnace of a spray type slag manufacturing apparatus to which the slag dissolving system according to the present invention is applied. The melting furnace has a predetermined accommodation space, and a refractory 310 for enduring high temperature on the inner surface surrounds the inner surface. Further, the melting furnace of the present invention replaces a high temperature to constitute a water-cooling type of cooling the structure. In the melting furnace except for the refractory material, a cooling structure 320 having a predetermined thickness is provided. Preferably, the basic structure of the melting furnace is made of SUS, and a cooler is provided in the inside of the furnace to introduce a water-cooled cooling system, and a cooling unit 330 for supplying cooling water to the cooling furnace.

On the other hand, the melting furnace containing the slag melt is mechanically controlled to secure the up / down driving and tilting driving.

The melting furnace according to the present invention is mechanically coupled to the driving means 400 constituted by the present invention. It can be combined with a separate driving means instead of a structure fixedly connected to the slag manufacturing apparatus, and can be separated from the manufacturing apparatus for a water-chain slag if necessary.

The driving means 400 is constituted by a lift portion 410 capable of moving up and down the melting furnace and a tilting portion 420 capable of tilting driving respectively and the elevating portion and the tilting portion adopt a cylinder of pneumatic or hydraulic type It is possible through a mechanical mechanism. Also, as shown in the present invention, a motor driving system can be adopted, and any structure can be used as long as it can raise, lower and tilt the melting furnace by mechanical elements. Such a design modification can be easily carried out by those skilled in the art.

The lifting and tilting drive is for powdering the slag dissolved in the melting furnace by means of the water chain. In the process of dissolving the slag, the slag is continuously melted in the downwardly driven state, and then the melted slag is pulverized The melting furnace itself is tilted to operate the water chain means at the same time as it is poured to the outside.

FIG. 5 is a view showing a water chain operation state of an injection type slag manufacturing apparatus to which the slag dissolving system according to the present invention is applied, and FIG. 6 is a view showing a water stranding means of the injection type slag manufacturing apparatus according to the present invention.

The mill chain means 500 according to the present invention is located on the lower side of the discharge port (not shown) of the melting furnace when the melted slag is pivoted and tilted. The water jetting means 500 includes an air nozzle 510 and a cooling water nozzle 520 for jetting a large number of pneumatic and cooling water and includes air supply means 530 for supplying air to the air nozzle, And a cooling water supply unit 540 for supplying cooling water to the cooling water supply unit 540.

At this time, although the air nozzle and the cooling water nozzle for precise control of the resin chain system are separately formed as necessary in the present invention, only the cooling water may be injected according to the designing method.

Further, in the present invention, the angle control means 540 for controlling the angle of the nozzle is further configured. The angle control means is physically coupled to a plurality of air nozzles and a cooling water nozzle, and then mechanically coupled to a driving device such as a motor to control the angle or the rotational direction. In addition, the angle control and direction control of the nozzle can be variously controlled according to the characteristics of the molten slag and the powder particle size, and a system capable of actively controlling the optimum parameters can be constructed.

Meanwhile, as described above, the apparatus of the present invention in which the dissolving system and the water chain system are integrally constructed can control the system through the control signal values programmed by the first control unit and the second control unit, thereby enabling a comprehensive system operation. The slag mixed with the acidic oxide and the basic oxide contains a large amount of silica, and among these, 10 to 20% is pure iron. For this reason, the molten slag has a high specific gravity of iron (Fe) settling down to the bottom, and when it melts in the water chain, the melted iron is preferentially discharged when the melting furnace is tilted.

Therefore, in the present invention, it is possible to realize the necessary slag pulverization process by controlling the shredding means in addition to the tilting control by the stepwise inclination. As the most basic control method, two-step control can be introduced. As mentioned above, to obtain the iron (Fe) powder first, the degree of inclination and the slope time (operation time application relative to the slag capacity) An operating signal can be programmed and controlled to obtain an optional powder.

The present invention thus constituted is capable of realizing a fully automatic system from melting to water-chain slag manufacturing in a single apparatus by applying an efficient melting system of slag generated in the steel industry and a chain- As a result, it is possible to expect a widespread effect on the relevant industrial market by narrowing the process constraints such as the transfer or the introduction of a separate secondary process system.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. On the contrary, those skilled in the art will appreciate that many modifications and variations of the present invention are possible without departing from the spirit and scope of the appended claims. And all such modifications and changes as fall within the scope of the present invention are therefore to be regarded as being within the scope of the present invention.

100:
110: Hopper
120: Screw
200: Electrode
210: heating furnace
220: Heating heater
300: melting furnace
310: Refractory
320: cooling furnace
330:
400: driving means
410:
420: tilting portion
500: spindle means
510: air nozzle
520: Cooling water nozzle
530: air supply means
540: Cooling water supply means
540: angle control means
600:
610:
620:

Claims (12)

A supply unit for supplying the collected slag by a predetermined amount;
At least two electrodes for melting the slag supplied from the supply unit through an arc discharge;
A slag melting material which melts and falls in the electrode rod is received, a refractory material is provided on the receiving surface,
A driving means for selectively driving the melting furnace in which the slag melt is accommodated, the upper and lower elevating and lowering driving means and the tilting driving means;
A saw chain means for spraying the molten slag toward the slag molten material discharged as a tilting melt through the driving means to cool / powder the molten slag; And
And a control unit for controlling supply control of the supply unit, electrical control for operating the electrode, drive control of the drive unit, air pressure or cooling water jetted from the water jetting unit, or jetting conditions including both of them A spray - type slag manufacturing system applying a slag dissolution system. The apparatus according to claim 1,
A hopper for injecting slag supplied from the outside in a predetermined amount, and a feed screw for feeding and supplying the slag injected into the hopper, wherein the slag dissolving system is applied. The slag manufacturing apparatus according to claim 2,
Further comprising a heating furnace located at an upper side of the electrode and for primarily heating slag supplied through the feed screw,
Wherein the heating furnace comprises a slag melting system in which an electric heater is formed in a space to primarily heat slag supplied and fed, and free fall in the heating furnace melts by arc discharge generated in the electrode. The plasma display apparatus according to claim 1 or 3,
Wherein the slag dissolving system has a structure in which two electrode rods face each other and are arranged side by side. The method according to claim 1,
A slag dissolving system using a slag dissolving system comprising a SUS material and having a cooling path for cooling the interior of the double structure to receive water cooling and having a structure in which cooling water is supplied and circulated by an external cooling means. 2. The apparatus according to claim 1,
And is connected to and supports the melting furnace of a predetermined size,
A connecting point connected to the melting furnace in a structurally rotatable manner and a spray type slag manufacturing apparatus applying a slag dissolving system for realizing up / down driving and tilting driving of the melting furnace by pneumatic or hydraulic type elevating or tilting driving of the driving means . 2. The image forming apparatus according to claim 1,
An air supply device for supplying air from the outside and a cooling water supply device for supplying cooling water so that the control part controls the air supply device And the cooling water supply means are controlled so that air and cooling water are sprayed to the slag dissolution system. 8. The image forming apparatus according to claim 7,
Further comprising an angle control means for mechanically controlling an injection angle of the air nozzle and the cooling water nozzle through the control unit through the control of the control unit. The apparatus of claim 1,
A first control unit for controlling a screw configured with the supply unit and an applied power source applied to the electrode,
And a second control unit for controlling the spraying conditions of the water jetting means. A supply unit for supplying the collected slag by a predetermined amount;
At least two electrodes for melting the slag supplied from the supply unit through an arc discharge;
A slag melting material which melts and falls in the electrode rod is received, a refractory material is provided on the receiving surface,
A driving means for selectively driving the melting furnace in which the slag melt is accommodated, the upper and lower elevating and lowering driving means and the tilting driving means;
A saw chain means for spraying the molten slag toward the slag molten material discharged as a tilting melt through the driving means to cool / powder the molten slag; And
And a control unit for controlling supply control of the supply unit, electrical control for operating the electrode, air pressure or cooling water jetted from the water-jetting unit, or spraying conditions including both of them, and a spray type slag manufacturing apparatus using the slag dissolving system Respectively,
A first step of controlling the tilting angle of the melting furnace in a first step by controlling the driving means in a stepwise manner to discharge the molten slag melt to the outside in the melting furnace;
A second step of primarily controlling the air injection and the cooling water injection condition of the water chain means according to the tilting angle of the melting furnace;
A third step of secondarily controlling a tilting angle of the melting furnace after the first step is controlled; And
And a fourth step of secondarily controlling the air injection and the cooling water spraying conditions, which are included in the water-jetting means, after the third step, and a fourth step of controlling the spraying and cooling water spraying conditions. 2. The method of claim 1, wherein the second and fourth steps comprise:
And controlling the angle of the air nozzle and the cooling water nozzle, wherein the slag dissolving system is used. The method according to claim 1, wherein, before the first step,
And a tilting step of raising and lowering a predetermined height in order to ensure a difference in height of molten slag due to the tilting of the melting furnace, wherein the slag dissolving system is applied.

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