JPH09105589A - Metal melting furnace and metal melting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal melting furnace and a method for melting metal capable of controlling the charging speed of a metal material from a preheating part to a melting part to an optimum range and efficiently melting the metal material only by an oxygen burner. SOLUTION: A preheating part 23 for preheating a metal material is provided above a melting part 22 provided with an oxygen burner 21. The restricted part 24 of an inside diameter smaller than that of the melting part 22 and the preheating part 23 is provided between the melting part 22 and the preheating part 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal melting furnace and a metal melting furnace for melting scraps of iron, copper, aluminum, etc., ingots, etc. only with an oxygen burner using oxygen or oxygen-enriched air as a combustion-supporting gas. Regarding the method.

[0002]

2. Description of the Related Art Fossil fuel is burned by an oxygen burner using oxygen or oxygen-enriched air as a combustion-supporting gas, and the heat of combustion burns scraps of iron, copper, aluminum, etc. and metal There is known a metal melting furnace that melts. As a melting furnace using such an oxygen burner, for example, JP-A-56-501810, JP-A-1-215919, JP-A-2-93012, JP-A-5-271804, 5-27
No. 1807 and the like.

Generally, these melting furnaces are provided with a melting part for melting the metal raw material with an oxygen burner and a preheating part for preheating the metal raw material. However, JP-A-56-501810 and Japanese Patent Laid-Open No. 1-215919. The metal melting furnace described in the publication has a preheating section above the melting section for preheating the metal raw material for the next charge through an openable iron grid. However, the metal melting furnace in which the iron grate is provided above the melting part needs to be cooled with water or the like because the iron grate is exposed to high heat, which causes not only a large water cooling heat loss but also a severe environment. For this reason, there are drawbacks such as water leakage and abnormal opening and closing of the iron grate.

Further, the melting furnace described in the above-mentioned Japanese Patent Laid-Open No. 5-271807 is of a so-called reverberatory furnace type, and the metal raw material is preheated by the exhaust gas from the melting section through an inclined passage provided on the side wall of the furnace. While being stirred, it is thrown into the melting section by gravity. However, in this case, the high-temperature exhaust gas tends to flow in the upper space of the inclined passage, which is the preheating section, and it is difficult to sufficiently preheat the metal material falling on the lower side of the inclined passage. It was also difficult to control the falling speed because the metal raw material was charged by falling.

Generally, in a melting furnace integrally provided with a preheating part for the metal raw material, the rate of charging the metal raw material from the preheating part to the melting part greatly affects the thermal efficiency. That is, the charging rate of the metal raw material is preferably substantially the same as the melting rate in the melting section, and if the charging rate of the raw material is too fast, molten metal and undissolved metal are mixed in the lower part of the melting section, and In some cases, heat loss from the bottom of the furnace may cause the molten metal to re-solidify. Conversely, if the input speed is low, the time required for inputting the metal raw material becomes longer, so that more energy is consumed than necessary.

Further, in the metal melting furnace, after melting the metal raw material, it is necessary to discharge the molten metal in the melting section to a ladle or the like. In the case of a relatively small melting furnace, the whole furnace is tilted. The hot water is discharged from a hot water outlet provided on one side of the melting section. However, in the case of a large melting furnace, there are problems such as the space for tilting the entire furnace and the problem that the driving device becomes large.Therefore, a tap hole is provided at the bottom of the melting part, I was trying to get out of the bath. For this reason,
Not only was the manufacturing cost increased due to the complicated structure of the melting portion, but the cost required for refractory maintenance and the like was also enormous.

Further, although such a metal melting furnace is generally formed by using a large amount of refractory material, since the basic unit of the refractory material due to damage affects the melting cost, molten metal is generated in the electric furnace. Water cooling is performed using a water cooling jacket except for the lower part of the furnace that comes into contact. This is because the structure of the electric furnace is such that the furnace wall is formed substantially vertically, the ceiling of the furnace is located higher than the bottom of the furnace, and the heat loss is small even if a water cooling jacket is used. It is possible because of this. Further, a melting furnace for melting a metal using an oxygen burner, for example, a metal melting furnace described in Japanese Patent Publication No. 56-501810, also partially cools the water, but the water-cooled portion is vertical. Only the furnace wall part.

As described above, in order to cool the metal melting furnace with water, the target parts were limited. In particular, in a metal melting furnace that uses an oxygen burner, where the distance from the bath surface of the molten metal to the ceiling is short, the heat radiation from the molten metal and the heat radiation from the burner are large, and heat loss from water cooling. Because of the large size, we had no choice but to use refractory materials. However, when refractory is used, the frequency of damage to the refractory is high because it is subjected to a large thermal shock during the melting stage of the metal raw material, and as a result, the refractory basic unit becomes large and the melting cost is greatly affected. Was there. In addition, manufacturing and repairing the insertion opening of the oxygen burner was extremely troublesome.

In addition, in the metal melting furnace using the oxygen burner, the mounting position of the oxygen burner and the jetting direction of the flame greatly affect the thermal efficiency. That is, in the melting of the metal raw material by the oxygen burner, not only the direct and rapid melting by the flame is performed, but also the preheating of the metal raw material by the combustion gas is performed. Therefore, in order to increase the thermal efficiency, it is necessary to sufficiently preheat the combustion gas and to rapidly melt the preheated metal raw material with a high-temperature flame.The melting rate, the preheating rate, and the melting from the preheating section are required. It is important to balance the feeding rate of metal raw materials into the parts.

For example, the melting performance can be improved by orienting the combustion flame of the oxygen burner toward the bottom of the furnace to some extent. However, in an actual melting furnace, the direction of the combustion flame is directed toward the bottom of the furnace. It is virtually impossible to install an oxygen burner on the furnace wall at a steep angle close to the vertical line, and the oxygen burner must be installed due to problems such as the burner insertion port manufacturing and interference between the oxygen burner accessory and the furnace outer wall. The angle is 10-2 with respect to the horizon on the side wall of the furnace.
It was about 0 degrees. For this reason, a dead zone is likely to occur in the peripheral portion, and it has been difficult to heat uniformly.

Further, when the metal raw material is melted by the combustion flame of the oxygen burner provided above the bath surface, the object to be heated may have a relatively low temperature in the initial solid state of the metal raw material in the melting portion. Although it is advantageous in terms of heat transfer, in the liquid state after the middle melting stage or in the coexistence state of solid and liquid, not only the heated object becomes high temperature, but also a limited heat transfer area of the upper surface of the bath can be expected. , Heat transfer becomes extremely disadvantageous. Therefore, improving the heat transfer characteristics after the middle stage of melting is an important issue when improving the efficiency of melting the metal raw material only with the oxygen burner.

Therefore, in Japanese Patent Laid-Open No. 5-271804, as a method for efficiently transferring heat from a high-temperature flame formed by burner combustion to an object to be heated, the combustion flame of an oxygen burner is rapidly transferred to the object to be heated. It is proposed to collide. However, even if the conditions of collision of the flame with the object to be heated are optimized, the bath surface becomes relatively smooth after the middle melting period, so there is a limit to the increase of the heat transfer area, and the object to be heated collides with the object to be heated. Since the temperature of the reflected gas is high, heat loss will occur.

Therefore, the first object of the present invention is to control the feeding rate of the metal raw material from the preheating portion to the melting portion within an optimum range, and to efficiently dissolve the metal raw material only with an oxygen burner. The object is to provide a metal melting furnace that can do so.

A second object of the present invention is to efficiently preheat the metal raw material, so that the metal raw material can be efficiently melted only by the oxygen burner, and molten metal can be easily discharged. To provide a metal melting furnace.

A third object of the present invention is to efficiently dissolve a metal raw material only with an oxygen burner, and
An object of the present invention is to provide a metal melting furnace which has a high heat load and can cool the unit of refractory by water cooling the portion where the oxygen burner insertion port and the like are provided.

A fourth object of the present invention is to control the feeding rate of the metal raw material from the preheating section to the melting section within an optimum range and to use the combustion flame of the oxygen burner in a well-balanced manner for melting and preheating the metal raw material. And to provide a metal melting furnace and a metal melting method capable of efficiently melting a metal raw material.

A fifth object of the present invention is to efficiently transfer the heat of the combustion flame of the oxygen burner to the molten metal even after the middle melting stage when the melting of the metal raw material has progressed to some extent.
An object of the present invention is to provide a metal melting method capable of efficiently melting a metal raw material only with the flame of an oxygen burner.

[0018]

In order to achieve the above object, a metal melting furnace of the present invention is a melting furnace for melting a metal raw material with a flame of an oxygen burner, which is installed above a melting section equipped with an oxygen burner. It is characterized in that a preheating part for preheating the metal raw material is provided, and a narrowed part having an inner diameter smaller than the inner diameters of the melting part and the preheating part is provided between the melting part and the preheating part.

As described above, by providing the narrowed portion between the melting portion and the preheating portion, it is possible to control the feeding speed of the raw material which is preheated in the preheating portion and naturally falls into the melting portion. In particular, the relationship between the cross-sectional area of the preheating portion and the cross-sectional area of the throttle portion is set so that the cross-sectional area of the preheating portion is in the range of 1.4 to 5 times, preferably 1.5 to 4 times the cross-sectional area of the throttle portion. By setting to, it is possible to introduce the metal raw material into the melting part at an optimum dropping speed (feeding speed). Further, the preheating state of the metal raw material in the preheating section changes depending on the relationship between the volume of the preheating section and the volume of the melting section, and the substantial volume of the preheating section is 0.4 to 3 times the substantial volume of the melting section. By setting the ratio to be twice, preferably 0.5 to 2 times, the metal raw material can be efficiently preheated and the thermal efficiency can be improved.

Further, by forming the melting portion and the preheating portion so that they can be separated from each other at or near the throttle portion, it is only necessary to separate the melting portion and the preheating portion and to tilt only the melting portion when tapping hot water. You can take a bath. Therefore, by providing the throttle portion and the preheating portion above the melting portion, even if the furnace height becomes high, it is possible to easily discharge the molten metal with a minimum tilting operation without discharging the molten metal from the furnace bottom. Especially,
Damage to the separation part can be prevented by forming the separation part of the melting part and the preheating part with a carbon refractory or by providing a water cooling jacket on the separation part.

Further, the upper part of the furnace wall of the melting part is formed with a water cooling jacket, and the angle of the inner wall surface of the water cooling jacket from the upper part of the furnace wall toward the narrowed part is 20 to the horizontal plane.
By setting the oxygen burner through the water cooling jacket while setting it in the range of 60 degrees, the heat loss due to water cooling can be minimized, the metal can be efficiently melted, and the refractory material in this portion can be efficiently melted. Since it is possible to significantly reduce the basic unit of refractory by being freed from the problem of damage, the melting cost can be reduced as a whole.

Further, the flame jet direction of the oxygen burner is 0.2 times the distance between the center of gravity of the melting portion and the burner mounting portion side on the bottom surface of the melting portion, and the distance between the center of gravity position and the inner wall of the oxygen burner mounting portion side. The oxygen burner is set by directing it into a circle centered on a point close to the distance, and setting the diameter of the circle to be 0.6 times the distance between the inner wall of the melter on the burner mounting side and the inner wall of the melter opposite to it. The combustion flame and the combustion exhaust gas can be efficiently used for melting and preheating the metal raw material, and the thermal efficiency can be improved.

The mounting height of the oxygen burner is
By setting the volume of the melting portion below the flame discharge port of the oxygen burner to be 0.35 to 0.9 times the volume of the entire melting portion, the combustion flame and the combustion exhaust gas of the oxygen burner are converted into metal raw materials. Can be efficiently used for melting and preheating, and the thermal efficiency can be improved.

Furthermore, by using an eccentric burner as the oxygen burner and rotatably providing the eccentric burner about the burner axis, the discharge direction of the combustion flame can be changed according to the melting stage of the metal raw material. Can be appropriately heated, the preheating state in the preheating section can be appropriately changed, and the dropping rate of the metal raw material from the preheating section to the melting section can be controlled.

Further, by providing the secondary combustion oxygen nozzle above the melting portion, it is possible to burn the unburned components and improve the thermal efficiency. Furthermore, by providing a molten metal stirring nozzle at the bottom of the melting portion, stirring of the molten metal can be promoted and the molten metal can be heated uniformly.

Next, the first metal melting method of melting the metal raw material of the present invention by the flame of the oxygen burner is to provide a preheating part for preheating the metal raw material above the melting part provided with the oxygen burner and to melt the metal raw material. Between the heating section and the preheating section, a metal melting furnace provided with a narrowed section having an inner diameter smaller than the inner diameters of the melting section and the preheating section is used, and an eccentric burner is used as the oxygen burner. It is characterized in that it is rotated about the burner axis in accordance with the melting stage of.

As described above, by using the metal melting furnace in which the narrowed portion having an appropriate inner diameter is provided between the melting portion and the preheating portion, the feeding speed of the raw material which is preheated in the preheating portion and falls into the melting portion. Can be controlled, and the metal raw material can be introduced into the melting part at an optimum falling speed (feeding speed).

By using an eccentric burner as the oxygen burner, the combustion flame can be discharged toward the bottom of the furnace, and the combustion flame and combustion gas of the oxygen burner can be efficiently dissolved and preheated in the metal raw material. Since it can be used, thermal efficiency can be improved. Further, by rotating the eccentric burner to change the discharge direction of the combustion flame, the discharge direction of the combustion flame can be changed according to the melting stage of the metal raw material, the metal raw material can be appropriately heated, and the preheating can be performed. The preheating state in the part can be changed as appropriate, and it is also possible to control the falling speed of the metal raw material from the preheating part to the melting part.

Further, in the second metal melting method of the present invention, a preheating part for preheating the metal raw material is provided above the melting part equipped with the oxygen burner, and between the melting part and the preheating part.
Using a metal melting furnace provided with a narrowed portion having an inner diameter smaller than the inner diameters of the melting portion and the preheating portion, a carbon material is added to the molten slag existing on the bath surface during the melting operation of the metal raw material, and the molten slag is formed. The feature is to let.

The combustion flame introduced from the oxygen burner into the molten slag collides with the surface of the molten metal bath to directly raise the temperature of the molten metal and then agitates the molten slag in the process of physically rising in the molten slag. While heating. At this time, the carbonaceous material is put into the molten slag, and by forming the molten slag into a forming state, the apparent volume of the molten slag increases, and the heat exchange efficiency between the high temperature gas and the molten slag increases,
Indirect temperature rise of the metal through the molten slag can be efficiently performed and heat loss is reduced.

The basicity γ of the molten slag, provided that
γ = (CaO) / (SiO ₂ ) is the melt processing temperature T
With respect to [° C.], “0.001T−0.6 ≦ γ ≦ 0.0
By controlling within the range shown by "025T-1", in forming the molten slag, the generation mode of the reaction gas and the physical properties of the molten slag can be controlled to obtain a stable forming state.

The melting part of the metal melting furnace according to the present invention is a part having the highest temperature in the whole furnace and contact with hot combustion gas is unavoidable. It is necessary to have excellent chemical resistance and erosion resistance, and a furnace material of a component type material containing magnesia is used. Specifically, magnesia, magnesia-carbon system, magnesia-chromia system and the like.

Further, the throttle portion must be excellent in durability at high temperature, mechanical strength, and wear resistance due to contact with high temperature combustion gas and impact due to dropping of metal raw material. -Use chromia type furnace material.

Further, the preheating portion may have a lower heat resistance than the melting portion and the narrowing portion, so that a furnace material made of alumina is used.

The oxygen burner used in the present invention is
It uses oxygen or oxygen-enriched air as a combustion-supporting gas and burns fossil fuels such as heavy oil, kerosene, pulverized coal, propane gas, and natural gas to form a high-temperature flame. As the oxygen burner, for example, an oxygen burner disclosed in Japanese Patent Publication No. 3-3122 or Japanese Patent Publication No. 7-43096 can be used, but the present invention is not limited thereto. Depending on the type of fuel, various structures can be used. The oxygen burner has advantages such as a smaller exhaust gas heat loss and a higher amount of heat adhering to the furnace, as compared with a burner using air as a combustion-supporting gas.

The eccentric burner used in the present invention as an oxygen burner is one in which the direction of discharge of combustion flame from the combustion nozzle at the tip of the burner body has an inclination angle with respect to the burner axis. As the eccentric burner, for example, as in the burner disclosed in Japanese Utility Model Laid-Open No. 59-103025, the flow path of the nozzle attached to the tip portion of the straight tubular burner main body is connected to the burner axis. It is possible to use those inclined at a predetermined angle, but the present invention is not limited to this, and various structures can be used according to the type of fuel and the like.

Further, as the rotating mechanism of the eccentric burner, for example, one having the structure disclosed in Japanese Utility Model Laid-Open No. 59-103025 can be used, but the present invention is not limited to this. Various structures can be used.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a first embodiment of a metal melting furnace to which the present invention is applied.

This melting furnace uses only the combustion heat of the oxygen burner 21 which uses oxygen or oxygen-enriched air as a combustion-supporting gas to produce iron,
It is for melting and reclaiming scrap such as copper and aluminum and metal. In the melting furnace, the melting part 22 is integrally provided in the lower part, the preheating part 23 is integrally provided in the upper part, and the narrowing part 24 is provided between the melting part 22 and the preheating part 23.

The melting portion 22 has an internal shape similar to that of a normal metal melting furnace such as an electric furnace, and is made of a magnesia-carbon type furnace material containing 5 to 20% by weight of carbon. There is. Further, on one side of the melting portion 22, a tap hole 26 for the melt 25 subjected to the melting treatment is provided.

The preheating part 23 is formed in a substantially cylindrical shape and is made of an alumina-silica type furnace material. A lid 28 having an exhaust port 27 is detachably attached to the upper opening of the preheating unit 23.

The narrowing portion 24 is provided to control the falling speed of the metal raw material 29 falling from the preheating portion 23 to the melting portion 22, and has an inner diameter smaller than the inner diameters of the melting portion 22 and the preheating portion 23. Has been formed. The throttle 24
Is made of magnesia-chromia based furnace material containing 10-30% by weight of chromia. It is preferable that the narrowed portion 24 and the large-diameter melting portion 22 or the preheating portion 23 are connected by oblique sides 30 and 31 to form a cone shape as shown in the drawing. It is possible to connect this part with a curved surface, but in the case of a furnace formed by lining a refractory, the work of lining the refractory becomes troublesome. When the hypotenuses 30 and 31 are close to the vertical, the height of the furnace becomes high, and when close to the horizontal, dead spaces may occur and the thermal efficiency may decrease. (Slope 30) is about 20 to 60 degrees, the bottom of the preheating unit 23 (Slope 3)
It is preferable to set 1) to about 20 to 70 degrees.

The oxygen burner 21 is installed by inserting one or a plurality of oxygen burners 21 into the insertion holes 32 provided in the peripheral wall of the melting portion 22, depending on the required melting capacity. Depending on the size of the portion 22 or the like, it can be set at a vertical portion of the furnace wall or at an appropriate position on the ceiling portion. Further, the oxygen burner 21 is provided so that the flame ejection direction is directed to the bottom of the melting part 22 so that the metal raw material 29 dropped in the melting part 22 can be melted from the bottom side of the melting part 22. . Fuel such as heavy oil and pulverized coal and a combustion-supporting gas are introduced into the oxygen burner 21 through unillustrated paths.

A typical dissolution pattern when iron scrap is melted only with an oxygen burner is shown in FIG. In FIG. 2, step 1 is a step of preheating the scrap filled in the furnace with the combustion gas from the burner. The exhaust gas temperature is low and the surface area of the metal is large, so that the oxidation rate is the highest. Step 2 is the stage where most of the scrap is melted and a small amount of unmelted remains in the lower part of the furnace.
The calorific value of the combustion gas is consumed for melting the unmelted portion, and the molten metal temperature is near the melting point. Also, since there is no scrap in the upper part of the furnace, the exhaust gas temperature rises,
The surface area of the metal is reduced and the oxidation rate is reduced. Step 3 is a step of raising the temperature of the molten metal by 100 ° C. from the melting point after the scrap is completely melted.

In the metal melting furnace in which the metal raw material 29 is melted by such a melting pattern, by providing the narrowed portion 24 having an appropriate size above the melting portion 22, the preheating portion 23 can be removed without providing the iron grid or the like. Since the dropping speed of the metal raw material 29 falling into the melting section 22 can be controlled to an optimum state via the throttle section 24, and the preheating section 23 can be provided immediately above the melting section 22, Step 1
The preheating of the metal raw material 29 in 1 can be efficiently performed.

That is, the squeezing portion 24 is provided above the melting portion 22.
By arranging the preheating section 23 in series through the preheating section 23,
Since it is possible to control the amount of raw material falling from the melting section 22 to the optimum speed, it is not necessary to provide a device for controlling the amount of raw material input such as a conventional iron grate, and a melting furnace of a simple structure can be used for iron and copper. , Scrap such as aluminum and metal can be efficiently melted, and the manufacturing cost and maintenance cost can be reduced by simplifying the structure of the furnace, and the thermal efficiency can be improved and the melting time can be shortened.

In the metal melting furnace having the above structure, the narrowed portion 2
The size of 4 can be appropriately set depending on the processing capacity of the furnace, the capacity of the oxygen burner, the type of metal raw material, the sizes of the melting section 22 and the preheating section 23, etc.
The cross-sectional area of the preheating portion 23 is 1.4 to 5 of the cross-sectional area of the throttle portion 24.
It is desirable to set it to be in the range of double, preferably 1.5 to 4 times. For example, if the cross-sectional area of the preheating portion 23 is less than 1.4 times the cross-sectional area of the narrowed portion 24, the falling speed of the metal raw material becomes too fast, and the effect of providing the narrowed portion 24 becomes difficult to obtain. When the cross-sectional area of 23 is more than 5 times the cross-sectional area of the narrowed portion 24, the metal raw material is less likely to drop and tends to be over-throttled.

Further, since the relationship between the substantial volume of the preheating section 23 and the substantial volume of the melting section 22 also affects the melting ability, the substantial volume of the preheating section 23 is set to the substantial volume of the melting section 22. It is desirable to set the volume within a range of 0.4 to 3 times, preferably 0.5 to 2 times the normal volume. For example, when the volume of the preheating section 23 is too small as compared with the volume of the melting section 22, most of the metal raw material is directly melted without undergoing preheating, and conversely when the volume of the preheating section 23 is too large. Since most of the input thermal energy is consumed for preheating, the thermal efficiency tends to decrease in any case.

The term "substantial volume" means that the scrap exists in the melting section 22 and the preheating section 23 when the scrap or the like is charged from the upper opening of the preheating section 23 before starting the melting process. It corresponds to the volume, and is different from the volume calculated from the dimensions.

FIG. 3 is a vertical sectional view showing a second embodiment of the metal melting furnace to which the present invention is applied. The same components as those in the metal melting furnace of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The metal melting furnace of the second embodiment is the same as the metal melting furnace of the first embodiment, except that a secondary combustion oxygen nozzle 33 is provided on the melting part 22 and the bottom of the melting part 22 is provided. A molten metal stirring nozzle 34 is provided.

That is, the secondary combustion oxygen nozzle 33 can be provided at an appropriate position on the vertical portion of the furnace wall or on the ceiling portion depending on the size of the melting portion 22 and the like. The secondary combustion oxygen nozzle 33 blows oxygen into the melting portion 22 to burn combustible components generated from the metal raw material, the auxiliary raw material, etc. at the time of melting to improve the thermal efficiency. The amount of oxygen blown from the secondary combustion oxygen nozzle 33 can be controlled by detecting exhaust gas components and the like online.

Further, the nozzle 34 for stirring the molten metal is the plug 3
5 and the receiving sleeve 36, and is provided on the furnace wall at the bottom of the melting portion 22. The molten metal stirring nozzle 34 blows a gas into the molten metal to stir the molten metal, thereby uniformly heating the molten metal. In this embodiment, a single tube type plug is used, but a thin tube composite type plug or a porous refractory type plug can also be used.

4 to 6 are vertical sectional views showing a third embodiment of the metal melting furnace to which the present invention is applied. The first
The same components as those in the metal melting furnace of the embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The metal melting furnace of the third embodiment is different from the metal melting furnace of the first embodiment in that the intermediate portion of the throttle portion 24 is
Separation part 37 for separating the melting part 22 and the preheating part 23
Is provided.

In this embodiment, the melting portion 22 and the preheating portion 23 can be separated by providing the separating portion 37. Therefore, when the molten metal in the melting portion 22 is tapped, it is shown in FIG. As described above, the melting portion 22 is separated from the preheating portion 23 and only the melting portion 22 is inclined, so that the hot water discharge operation can be performed. Therefore, even if the furnace height is increased by providing the preheating section 23 above the melting section 22 via the narrowed section 24, it is not necessary to tilt the entire furnace, and therefore, there is no tapping from the furnace bottom, You can operate the hot water in a small space.

Further, by providing the separating portion 37 in the narrowed portion 24 having a relatively small inner diameter or in the vicinity thereof, particularly in the portion of the narrowed portion 24 having the smallest inner diameter, diffusion from the melting portion 22 when the two are separated. The amount of heat can be reduced.

Here, since the apparatus for inclining the melting portion 22 usually preferably supports the melting portion 22 which is a heavy object in the vicinity of the position of the center of gravity thereof, in this case, the melting portion 22 is simply supported. It cannot be tilted. Therefore, when performing the above-described tapping operation, first, the preheating part 23 and the narrowing part 24 are separated from the melting part 22 by rising above the separating part 37, and then the tilting device is operated to operate the melting part 22. Make it tilt. Note that the melting portion 22 and the squeezing portion 24 may be tilted after lowering the portions below the separating portion 37. Further, if the center of rotation of the melting portion 22 is set to an appropriate position, it is possible to perform hot water discharge by simply tilting the melting portion 22, and further, the melting portion 2
2 or the preheating unit 23 may be moved horizontally.

By providing the separating portion 37 in this way, tapping operation can be easily performed in a limited space, but in the vicinity of the squeezing portion 24 where the separating portion 37 is provided, the melting generated during melting. Since it is provided in a place where metal splash and slag are easily attached, the melting portion 22 and the preheating portion 2
When separating 3 and 3, the refractory on the inner surface of the furnace may be damaged as well as the deposits are separated.

Therefore, it is preferable that the separating portion 37 has a structure in which the splash or slag of the molten metal is unlikely to adhere and damage is unlikely to occur. Therefore, in the metal melting furnace shown in FIG. 4 and FIG. 5, a carbon-based refractory (for example, MgO—C) 38, which is a refractory in which the splash or slag is hard to be attached and is hard to be damaged, in the part of the separation part 37 It is formed by. Further, in the metal melting furnace shown in FIG. 6, a water cooling jacket 39 is provided at the separation part 37. By using the carbon-based refractory material 38 and the water-cooled jacket 39 in this way, it is possible to prevent the refractory material from being damaged in the separating portion 37. It is also possible to provide a water cooling tube instead of the water cooling jacket.

FIG. 7 is a vertical sectional view showing a fourth embodiment of the metal melting furnace to which the present invention is applied. The same components as those in the metal melting furnace of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The metal melting furnace of the fourth embodiment is the same as the metal melting furnace of the first embodiment, except that the upper part of the furnace wall of the melting part 22 is formed by the water cooling jacket 40, and the narrowed part 24 is formed from the upper part of the furnace wall. The angle of the inner wall surface (the hypotenuse 30) of the water-cooling jacket facing toward is set in the range of 20 to 60 degrees with respect to the horizontal plane, and the oxygen burner 21 is provided through the water-cooling jacket 40.

That is, the squeezing portion 2 above the furnace wall of the melting portion 22.
4 and the furnace wall of the preheating section 23 are formed by the water cooling jacket 40, and the furnace wall below the melting section 22 with which the molten metal comes into contact is formed by a refractory material. The ceiling part of the melting part 22 in this water cooling jacket 40 (the hypotenuse 30)
Is formed in a cone shape that converges from the peripheral wall of the melting portion 22 toward the inner circumference of the narrowed portion 24 at an ascending angle in the range of 20 to 60 degrees, and the bottom portion (the hypotenuse 31) of the preheating portion 23 is the narrowed portion. It is formed in a cone shape that converges downward toward the inner periphery of 24.

The rising angle of the lower surface of the ceiling part has a great influence on the melting performance, the thermal efficiency and the heat loss in the melting part 22, and when the rising angle is in the range of 20 to 60 degrees, Cooling loss and thermal efficiency are balanced, and efficient melting operation can be performed.

That is, when the rising angle is smaller than 20 degrees, the heat transfer from the flame of the oxygen burner 21 or the metal melting surface to the water cooling jacket 40 becomes large and the water cooling heat loss becomes large, and the rising angle becomes 60 degrees. If it is made larger, the water cooling heat loss becomes smaller, but the heat transfer from the oxygen burner 21 to the metal becomes smaller, and as a result, the thermal efficiency is lowered.

Therefore, the ascending angle of the ceiling is 20 to
By setting it in the range of 60 degrees, it is possible to minimize the deterioration of melting capacity and thermal efficiency and perform water cooling, and it is possible to greatly reduce the cost of refractory, so subtract the decrease in thermal efficiency Also, the metal melting cost can be reduced as a whole. Further, although repairing or replacing a damaged refractory requires a considerable number of days, the water-cooling jacket 40 requires almost no repair.
The operating rate of the furnace is also improved.

FIGS. 8 and 9 are views showing a fifth embodiment of the metal melting furnace to which the present invention is applied. FIG. 8 is a vertical sectional view of the metal melting furnace. FIG. 9 is a diagram for explaining the flame ejection direction and mounting height of the oxygen burner. still,
The same components as those in the metal melting furnace of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The metal melting furnace of the fifth embodiment is related to the embodiment in which the oxygen burner 21 in the metal melting furnace of the first embodiment is attached at an optimum position. That is,
In the present embodiment, the flame ejection direction of the oxygen burner 21 is set to 0.2 on the bottom surface of the melting portion from the position of the center of gravity of the melting portion to the side of the burner mounting portion, which is 0.2 The diameter of the circle is set to be 0.6 times the distance between the inner wall of the melting portion on the burner mounting portion side and the inner wall of the melting portion opposite to the inner wall of the melting portion. In addition, the mounting height of the oxygen burner 21
The volume of the melting portion below the flame outlet of the oxygen burner 21 is set to a position that is 0.35 to 0.9 times the volume of the entire melting portion 22.

Since the condition of collision of the flame formed by the combustion of the oxygen burner 21 with the object to be heated (metal raw material or molten metal) has a great influence on the efficiency of heating and melting, it is sufficient before the collision with the object to be heated. Combustion and increasing the kinetic energy of the flame are important. For example, the combustion rate until the flame hits the object to be heated decreases if the position of the discharge port of the burner is lowered too much, but if the position of the discharge port is raised too much to increase the combustion rate, the flame when hitting the object to be heated Kinetic energy (collision speed) of will decrease.
In addition, in order to increase the kinetic energy, in addition to the amount of combustion gas itself and the relative position of the flame and the object to be heated, the installation angle of the burner (flame ejection angle) is also important, and the inclination angle is too small. And kinetic energy can not be raised enough. On the other hand, the larger the inclination angle, the more easily the kinetic energy of the flame is transmitted to the object to be heated, and the effect of promoting the dissolution by the stirring action or the like can be expected. In this case, the oxygen burner 21 should be installed in the space above the molten metal in the melting section 22 because it is necessary to install the oxygen burner 21 while avoiding burner melting loss due to contact with the molten metal and avoiding interference with the furnace body. There are naturally limits to the parts that can be used.

Therefore, although the flame ejection direction and the attachment position of the oxygen burner 21 are set according to the shape and size of the melting portion 22, as shown in FIG. At, the distance between the center of gravity O of the melting portion and the inner wall on the oxygen burner mounting portion A side is Ro, and the burner mounting portion A is
When the distance between the inner wall on the side and the inner wall opposite thereto is Do, the flame ejection direction of the oxygen burner 21 is determined by the center of gravity O of the melting portion.
From the oxygen burner mounting portion A side, the distance Ro of 0.2
The point is set so as to face a circle C having a diameter D which is 0.6 times the distance Do, centered at a point approached by a double distance R. This makes it possible to optimize the conditions under which the combustion flame collides with the metal.

The mounting height of the oxygen burner 21 is
By setting the volume of the melting portion below the discharge port of the oxygen burner 21 to be 0.35 to 0.9 times, preferably 0.45 to 0.80 times the volume of the entire melting portion 22. Further, the metal raw material can be dissolved more efficiently.

Here, when the bottom of the melting portion 22 is substantially circular, its diameter is Do, and its radius is Ro, the oxygen burner 2
The center position of the circle C, which is the flame ejection direction of No. 1, is 0.2Ro from the center of the melting portion (same as the center of gravity) to the burner mounting portion side, and the diameter of the circle C is 0.6Do.

For example, when the melting portion 22 has a substantially cylindrical shape, the height H of the discharge port (nozzle tip portion) of the oxygen burner 21 is 0.35 Ho to 0.9 with respect to the height Ho of the melting portion.
Ho, preferably 0.45Ho to 0.80Ho.
However, in reality, it may be slightly different depending on the shapes of the bottom surface and the ceiling surface of the melting portion 22.

FIG. 10 is a vertical sectional view showing a sixth embodiment of the metal melting furnace to which the present invention is applied. The same components as those in the metal melting furnace of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The metal melting furnace of the sixth embodiment is the same as the metal melting furnace of the first embodiment, except that an eccentric burner 41 is used as an oxygen burner, and the eccentric burner 41 is used as a rotating mechanism 4.
2 is provided so as to be rotatable around the burner axis. As the eccentric burner 41 and the rotating mechanism 42, as described above, for example, the burner and rotating mechanism disclosed in Japanese Utility Model Laid-Open No. 59-103025 can be used.

As described above, by using the eccentric burner 41, the mounting angle of the oxygen burner 1 is restricted,
Even if the mounting angle is small, the discharge direction of the combustion flame can be oriented at a large angle with respect to the bottom of the melting portion 22, so that the peripheral portion of the melting portion 22 can be uniformly heated without causing a dead zone. .

On the other hand, in order to quickly dissolve the metal raw material, the collision condition of the flame formed by the burner combustion with the object to be heated has a great influence on the efficiency of the heating and melting, and the flame causes the object to be heated. It is important to have sufficient combustion before the collision and to increase the kinetic energy of the flame. The combustion rate until the flame collides with the object to be heated decreases when the distance is too short, but when the distance is increased to increase the combustion rate, the collision speed decreases and the kinetic energy decreases. Further, in order to increase the kinetic energy, it is advantageous to increase the amount of the combustion gas itself and to increase the collision angle so as to approach the vertical direction in order to increase the heat transfer efficiency to the object to be heated.

Therefore, by using the eccentric burner 41 to direct the discharge direction of the combustion flame to the vertical direction,
In the initial stage of melting, it is possible to delay the softening and melting of the base portion of the metal raw material 29 directly connected in a tower shape from the melting portion 22 to the preheating portion 23, and by delaying the fall of the metal raw material 29 to some extent, sufficient preheating can be performed. While you can
In the latter stage of melting, the kinetic energy of the combustion flame at the time of collision is easily transferred to the molten metal, and the effect of promoting melting is improved by the stirring action of the molten metal and the like.

Further, as in the first metal melting method of the present invention, the eccentric burner 41 is rotated around the burner axis in accordance with the melting stage, and the discharge direction of the combustion flame is changed. Improve the preheating part 2
It is possible to control the falling speed of the metal raw material 29 from the position 3.

FIG. 11 is a vertical sectional view showing an embodiment of a metal melting furnace for explaining the second metal melting method of the present invention. The same components as those in the metal melting furnace of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The second metal melting method of the present invention uses the metal melting furnace shown in FIG. 11 to introduce carbonaceous material into the molten slag existing on the bath surface during the melting operation of the metal raw material, and melt the molten slag. The heating efficiency is improved by forming the slag 43 (forming slag) 43 in the forming state. The basicity γ of the molten slag is 0.001T-0.6 ≦ γ ≦ with respect to the molten metal treatment temperature T [° C].
A stable forming state can be obtained by controlling within the range indicated by 0.0025T-1.

That is, in the metal melting furnace shown in FIG.
When the metal raw material is melted by the combustion flame of the oxygen burner 21, the carbonaceous material is added to the molten slag existing on the bath surface of the melting part 22 after the middle melting stage, and the forming slag 43 is formed.
And

The forming of the molten slag has been studied as a secondary heat transfer technique in the iron ore smelting reduction method as a heat transfer promoting method utilizing the forming slag state. This heat transfer promotion method is a method in which carbon monoxide gas generated in the primary reaction of iron ore and carbonaceous material is reacted with oxygen gas added in the slag or above the slag, and secondarily burned to carbon dioxide. When the secondary combustion is performed in the slag, the carbon dioxide gas, which has become high in temperature due to the formation reaction, exchanges heat with the slag while rising in the forming slag to raise the temperature of the slag.

The present invention has made the heat transfer efficiency in this forming state more effective. The high temperature flame of the oxygen burner 21 penetrates into the forming slag 43 to reach the vicinity of the bath, and then from the slag. Heat is transferred over the entire residence time until it escapes, and the amount of heat transferred to the slag can be further increased as compared with the method by the secondary combustion.

Usually, when a metal raw material is melted by a combustion flame of an oxygen burner, the flame of the oxygen burner collides with the bath surface of the molten metal to directly raise the temperature of the metal, and then the liquid state existing on the bath surface is maintained. While ascending in the slag, heat is exchanged with the slag to raise the temperature of the slag and cause the metal to circulate and flow, thereby indirectly raising the temperature of the metal via the slag.

The state in which the combustion gas passes through the slag layer has a great influence on this indirect temperature rise, and the higher the slag height is, the more advantageous it is. However, in terms of thermal problems and refractory meltdown, the operation is performed. Increasing the amount of slag, which is disadvantageous, should be avoided. Therefore,
By adding carbonaceous material to the molten slag and continuously reacting the reducing components such as iron oxides in the slag with the carbonaceous material, and making the slag into a forming state by the generated gas, the apparent volume of the slag is reduced. Therefore, the efficiency of heat exchange between the combustion gas and the forming slag 43 can be increased, and the temperature of the metal indirectly through the forming slag 43 can be efficiently increased.

That is, the combustion flame from the oxygen burner 21 passes through the forming slag 43 and collides with the bath to directly raise the temperature of the bath, and then physically rises in the forming slag 43 to generate slag. Although the temperature rises, the apparent volume of slag increases due to forming, so the residence time of the combustion gas that passes through the slag becomes longer, and the amount of heat transfer to the slag can be increased and the slag generated by the combustion gas Stirring and circulating flow can also be effectively performed. Therefore, heat can be efficiently transferred from the slag to the bath, and the melting time can be shortened and the thermal efficiency can be significantly improved. Further, since iron oxide is reduced by the carbonaceous material, the iron yield is also improved.

As the carbonaceous material, powdery or granular coke can be used, and its addition amount varies depending on the amount of slag generated, the layer thickness, etc. The range of 10 kg is suitable, and if the addition amount is small, a sufficient forming state cannot be obtained, and conversely, if the addition amount is too large, the cost of the carbonaceous material increases.

Here, in order to obtain a stable forming state, it is important to appropriately control the generation mode of the reaction gas and the physical properties of the slag, that is, the gas generation rate, the bubble diameter, the viscosity and the surface tension of the slag. is there. For example, when reducing the reducible oxide in the molten slag to generate bubbles of carbon monoxide, it is effective to use fine carbonaceous material to obtain fine bubbles. In order to obtain the desired amount, it is effective to continuously add an appropriate amount of carbonaceous material.

Further, when melting the metal raw material, it is necessary to efficiently perform heating from the solid state to the liquid state through the coexisting state of the solid liquid. The bath temperature when heating the molten metal 25 through the forming slag 43 varies depending on the carbon concentration and the like in the case of iron, for example, but a part of the iron raw material begins to melt and becomes smooth about 100.
The temperature range is from 0 ° C to 1300 to 1600 ° C or higher at which hot water can be discharged. As a result of various studies to stably maintain the forming state of the slag within this temperature range, it was found that it is effective to control the basicity of the slag according to the temperature. That is, the basicity γ = (CaO) / (SiO ₂ ) of the molten slag is defined as the molten metal treatment temperature T
0.001T-0.6 ≦ γ ≦ 0.00 with respect to [° C.]
By controlling within the range shown by 25T-1, a stable forming state can be obtained, and the heat energy of the combustion flame of the oxygen burner 21 can be efficiently transferred to the molten metal.

The present invention is not limited to the above-described embodiments, and it goes without saying that the embodiments may be combined.

[0092]

【Example】

Example 1 Using a metal melting furnace having a structure shown in FIG. 1, an experiment was carried out to melt 1 ton of iron scrap and confirm the effect of the narrowed portion. The melting portion was formed of magnesia-carbon (10%), the narrowing portion was formed of magnesia-chromia (20%), and the preheating portion was formed of alumina-silica (12%). The size of the melting portion was constant with a total height of 80 cm and an inner diameter of 90 cm. When 1 ton of iron is melted in this melting part, the bath surface height is about 22 cm.
Becomes In addition, since the size of the melting part is constant,
The volumes of the preheating part and the melting part occupied by the scrap when the scrap is charged, that is, the ratio of the substantial volume of the preheating part to the substantial volume of the melting part is substantially constant, and in this case, it is about 1: 1. Therefore, when iron scrap is charged into the furnace through the upper opening of the preheating section, about 500 kg of scrap exists inside the preheating section and the melting section.

Three oxygen burners were installed on the slanted ceiling of the melting part in a state of being slanted about 60 degrees with respect to the horizontal plane, toward the center of the furnace bottom. Pulverized coal was supplied as a fuel to each oxygen burner at 35 kg / h, and high temperature oxygen at about 600 ° C. was supplied as a combustion supporting gas at an oxygen ratio of 1.0. Pulverized coal was transported by air. The flame temperature of this oxygen burner was about 2800 ° C. at the highest temperature, and the flame length was 70 cm.

Then, the ratio of the diameter (cross-sectional area) of the preheating portion to the diameter (cross-sectional area) of the narrowed portion was variously changed to perform the melting treatment of 1 ton of iron scrap (heavy scrap), and the tapping temperature was set to 1
With the temperature kept constant at 630 ° C., the drop rate of scrap, the time required for melting, and the thermal efficiency were measured. The height of the inner peripheral surface of the narrowed portion was about 20 cm. Also,
The ceiling surface of the melting section was connected to the throttle section with an inclination of about 30 degrees, and the bottom surface of the preheating section was connected to the throttle section with an inclination to prevent scrap from staying. The results are shown in Table 1 and FIG.
Shown in In addition, Experiment No. 8 in Table 1 is a comparative example in the case of using a metal melting furnace having no throttle portion.

[0095]

[Table 1]

In the table, the thermal efficiency was calculated by the following equation. η = HY / Q where η: Thermal efficiency H: Heat capacity per ton of metal after melting Y: Yield of melting Q: Burning heat quantity in a burner required to melt 1 ton of metal raw material

The drop control coefficient was calculated by the following equation. υ = 100T / t However, υ: Fall control coefficient t: Time from the start of combustion until all of the metal raw material charged into the metal melting furnace falls into the melting part T: Cross-sectional area of the preheating part is the cross-sectional area of the throttle part T when 1.5 times

As is clear from Table 1 and FIG. 12, when the ratio of the substantial volume of the preheating part to the substantial volume of the melting part is kept constant at about 1: 1, the cross-sectional area of the preheating part and It can be seen that the dissolution performance changes depending on the ratio with the cross-sectional area of the narrowed portion. From this, it can be seen that the scrap drop control coefficient, that is, the scrap drop speed, has a great influence on the melting performance, and if the cross-sectional area of the preheating part is made 6 times the cross-sectional area of the throttle part, the drop speed of the scrap becomes slow. If the ratio is 1.2 times, the scrap dropping speed will be too fast and the melting will not catch up, and the drawing will tend to be insufficient. From these results, when the cross-sectional area of the preheating portion is in the range of 1.4 to 5 times, particularly in the range of 1.5 to 4 times the cross-sectional area of the narrowed portion, the melting time is shortened and the thermal efficiency is improved. It can be seen that the improvement can be achieved, that is, the dissolving ability is improved.

Example 2 Next, the cross-sectional area of the preheating portion was made constant 1.5 times the cross-sectional area of the throttle portion, and the ratio of the substantial volume of the preheating portion to the substantial volume of the melting portion, that is, The same experiment was conducted by changing the ratio of the amount of iron scrap. Table 2 shows the results.
Shown in It should be noted that the throttle portion is calculated as a part of the preheating portion.

[0100]

[Table 2]

Example 3 An experiment in which 1 ton of iron scrap was melted using a metal melting furnace having the structure shown in FIG. 3, oxygen for secondary combustion was blown from an oxygen nozzle for secondary combustion, and the effect was confirmed. I went.
The same procedure as in Example 1 was performed except that the cross-sectional area of the preheating portion was 1.4 times the cross-sectional area of the narrowed portion.

From the secondary combustion oxygen nozzle, oxygen of 5 Nm ³ /
When h was blown in, the thermal efficiency improved from 47% to 52%. In addition, the exhaust gas heat loss was reduced from 53% to 33%, and the amount of heat deposited in the furnace was improved from 47% to 67%.

Example 4 Using a metal melting furnace having the structure shown in FIG. 7, 1 ton of iron scrap was melted and the thermal efficiency when a water-cooled jacket was used was measured. In addition, substantially the same as Example 2 except that the mounting angle of the oxygen burner was 40 degrees.

Then, the rising angle (tilt angle) of the ceiling surface of the melting part was variously changed, and the water cooling heat loss coefficient, the melting time and the thermal efficiency at that time were measured. Also, the same measurement was performed when the entire melted portion was formed of a refractory material. Table 3 shows the results. The water-cooling heat loss coefficient is a relative value with 100 when the rising angle is 30 degrees.

[0105]

[Table 3]

From the results shown in Table 3, when the entire melted portion is made of refractory and the rising angles are 25 ° and 30 °, that is,
If there is no water-cooling heat loss at this part, the ratio of the input heat amount effectively transferred to the molten metal, that is, the thermal efficiency is 50 to 51.
%Met. On the other hand, in the case of water cooling with the water cooling jacket, there were differences in water cooling heat loss, melting time, and thermal efficiency depending on the rising angle. For example, when the ascending angle is small, a large amount of heat from the molten metal is received, so that there is a reasonable tendency that the water cooling heat loss becomes large. However, there was no correlation between the magnitude of this water cooling heat loss and the dissolving ability, and there was a large difference in the dissolving ability between the rising angles of 15 ° and 20 ° and 60 ° and 70 °.

From this, it is judged that the influence of the water cooling heat loss becomes large when the rising angle is between 15 degrees and 20 degrees.
Between 70 and 70 degrees, it is judged that the influence of the behavior of the combustion waste gas in the melting part becomes large. Therefore, when the water cooling jacket is used to cool the melting portion with water, it is considered appropriate to set the rising angle of the ceiling portion within the range of 20 to 60 degrees. The thermal efficiency at this time is 4 to 8% lower than that of the refractory material, but relatively good performance of 43 to 46% is obtained. That is, although the thermal efficiency is reduced, the metal melting cost as a whole can be reduced in consideration of damage to the refractory material.

Example 5 Using a metal melting furnace having the structure shown in FIG. 8, three oxygen burners using heavy oil as a fuel and pure oxygen as a combustion-supporting gas were installed, and the positions and flames of the oxygen burners were installed. Change the ejection direction of 1 ton of iron scrap (heavy scrap), copper (bare metal)
1 ton, aluminum scrap (sash scrap) 400k
The thermal efficiency when each g was dissolved was measured. The melting portion has a total height of 70 cm and an inner diameter of 90 cm, and the rising angle of the ceiling surface is 30 degrees. In addition, the flow rate of the heavy oil is 3
The total was 90 liters per hour. Others are Example 2.
It was almost the same as.

The jet directions of the flames in the respective oxygen burners are shown in a, b, c, d, e, f, g, h, i in FIG.
Table 4 shows the respective thermal efficiencies when the heat is turned to. a to e are examples of the present invention, and f to i are comparative examples. However, the "-" display portion in the table was not measured.

[0110]

[Table 4]

Example 6 Six oxygen burners similar to those in Example 5 were installed in a melting section having a ceiling height of 120 cm, an inner diameter of 160 cm, and an inclination angle of 30 degrees to melt 5 tons of iron scrap (heavy scrap). Then, the thermal efficiency was measured in the same manner as in Example 5. Table 5 shows the results. The flow rate of heavy oil was 400 liters per hour for the total of six oxygen burners.

[0112]

[Table 5]

Example 7 In Example 5 and Example 6, the oxygen burner was changed to one using pulverized coal as a fuel, and the pulverized coal supply rate was 90 kg / hr in a 1 ton furnace and 400 kg / hr in a 5 ton furnace. The thermal efficiency when iron scrap (heavy scraps) was melted was measured in the same manner except that Table 6 shows the results.

[0114]

[Table 6]

Example 8 In Examples 5 and 6, the thermal efficiency when iron scrap (heavy scrap) was melted by changing the mounting height of the oxygen burner was measured. Table 7 shows the results. The ratio in the table indicates the volume ratio of the melting portion below the oxygen burner discharge port, where the volume of the entire melting portion is 1.

[0116]

[Table 7]

In Examples 5 to 8 described above, in order to clarify the difference due to the difference in the ejection direction of the flames of the oxygen burners, the ejection directions of the flames of the three or six oxygen burners were changed in each of the oxygen burners. Same criteria (a ~
Although set in i), when a plurality of oxygen burners are used, it is possible to arbitrarily set the ejection direction of the flame in each burner. For example, when three oxygen burners are used, each burner is replaced with a,
The flames may be ejected in different directions as in b and c, and it is possible to implement them in an appropriate combination. In this case, the stirring action after melting (disturbance of the molten metal) may be greater than when the flame ejection direction of all oxygen burners is the same direction, and the raw materials are hardly soluble or the molten metal is uneven. In some cases, the dissolution time may be shortened in the case where the solubility is large.

Example 9 Using a metal melting furnace having the structure shown in FIG. 10, 1 ton of iron scrap (heavy scrap), copper scrap (pure copper wire scrap)
1 ton, aluminum scrap (sash scrap) 400k
The thermal efficiency when each g was dissolved was measured.

The oxygen burner was attached to the melting part at an angle of 15 degrees with respect to the horizontal line due to restrictions due to interference between the burner attachment part and the furnace body. Then, the thermal efficiency was measured for each of the general burner whose combustion flame discharge direction is the burner axis direction (0 degree), the burner whose discharge direction is eccentric by 25 degrees with respect to the burner axis direction, and the burner whose eccentricity is 40 degrees. . Further, in a burner in which the flame discharge direction is eccentric by 40 degrees, the burner rotates right about the axis every 3 minutes from the start of temperature increase to the time when all the metal raw materials fall into the melting part, 20 degrees, 0 degrees, The thermal efficiency was similarly measured in the case of repeatedly rotating in the order of 20 ° left turn. Table 8 shows the results. In addition, other than that, Example 5 is used.
It was almost the same as.

[0120]

[Table 8]

Example 10 A burner using pulverized coal as a fuel was used as an oxygen burner, the mounting angle was 20 degrees, and the thermal efficiency when the discharge direction of the combustion flame from the burner was 0 degrees, 20 degrees, and 40 degrees. The measurement was performed in the same manner as in Example 9. Table 9 shows the results.

[0122]

[Table 9]

Example 11 Using a metal melting furnace having the structure shown in FIG. 11, three oxygen burners using heavy oil as a fuel and pure oxygen as a combustion-supporting gas were installed at an inclination angle of 40 degrees with respect to the horizontal plane. Then, the thermal efficiency when 1 ton of iron scrap (heavy scrap) was melted was measured. The melting portion has a total height of 70 cm and an inner diameter of 90 cm, and the rising angle of the ceiling surface is 30 degrees. Further, the flow rate of heavy oil was set to 90 liters per hour for a total of three oxygen burners. Oxygen supplied 180 Nm ^{3 /} h. Others were substantially the same as in Example 2.

The time required from the raw material in the preheating section dropping into the melting section to the formation of slag until the carbonaceous material was added and the molten metal was tapped at 1630 ° C. Melting time), iron yield, and thermal efficiency were measured. The carbonaceous material used is coke powder or granules having a carbon content of 90% or more, and the coke powder having a grain size of 3 mm under is used, and 100 g, 200 g, 300 g / min.
g was added continuously. 10 to 10 coke grains
Using a particle size of 30 mm, 1 kg was added every 5 minutes. The results are shown in Table 10 including the case where the carbonaceous material was not added. The molten metal at the time of tapping has a carbon content of 0.0
It was a composition of low carbon molten steel of 3 to 0.07%.

[0125]

[Table 10]

Example 12 Using the same melting furnace as in Example 11, melting operation was performed by changing the basicity of the slag. The metal raw material used was a mixture of steel scrap and pig iron metal to 1 ton. In this case, the higher the carbon concentration in the molten metal, the more molten it will be from a relatively low temperature, and the molten metal can be discharged at a lower temperature. The basicity of the slag was adjusted using a flux containing burned lime and silica sand. The carbonaceous material is the same coke powder as in Example 11, and is 200 g / min.
Was added continuously. Then, the state of forming at each basicity was observed, and the total dissolution time and thermal efficiency were measured. In addition, the judgment of the quality of forming is
The stability was obtained when the forming state was maintained for 50% or more during the treatment after dropping the raw materials. The results are shown in Table 11.

[0127]

[Table 11]

[0128]

As described above, in the metal melting furnace of the present invention, since the preheating part is provided above the melting part through the throttle part, the introduction of the raw material which is preheated in the preheating part and falls into the melting part. The speed can be controlled, and scraps of various metals and metal can be efficiently melt-processed only with an oxygen burner, and various scraps can be reused at low cost. In particular, the cross-sectional area of the preheating portion is 1.4 to
In the range of 5 times, and / or by setting the substantial volume of the preheating section to 0.4 to 3 times the substantial volume of the melting section, even in a small-scale melting furnace, it is as high as 50% or more. Thermal efficiency can be achieved and excellent dissolution performance can be obtained.

Further, since the melting part and the preheating part can be separated at or near the throttle part, the tapping operation can be easily performed in a limited space without tilting the entire furnace.

Further, by forming the upper portion of the melting portion with a water cooling jacket, the refractory unit consumption can be greatly reduced, and the metal melting cost as a whole can be greatly reduced.

Further, by directing the flame ejection direction of the oxygen burner provided in the melting portion within a specific circle, it is possible to optimally control the melting and preheating of the metal raw materials and efficiently melt various metal raw materials. . Furthermore, by setting the burner mounting height within a specific range, the thermal efficiency can be further improved, and a particularly high effect can be obtained for melting a metal raw material such as iron having a high melting point. When a plurality of oxygen burners are used, it is possible to shorten the melting time by appropriately combining the flame ejection directions of the oxygen burners.

Further, as the oxygen burner, an eccentric burner whose discharge direction of the combustion flame from the combustion nozzle is substantially at an angle with respect to the burner axis is used, and the eccentric burner is rotated, whereby the metal in the melting portion is rotated. Can be uniformly heated, and the melting and preheating of the metal raw material can be optimally controlled.

Further, by providing an oxygen nozzle for secondary combustion on the upper part of the melting portion, it is possible to burn unburned components and improve the thermal efficiency. Furthermore, by providing a molten metal stirring nozzle at the bottom of the melting portion, stirring of the molten metal can be promoted and the molten metal can be heated uniformly.

Further, by introducing a carbonaceous material into the molten slag to put the molten slag in a forming state and performing a melting operation with an oxygen burner, the heat energy of the combustion flame can be effectively transferred to the slag. The temperature of the molten metal can be efficiently raised via the. As a result, the melting time can be shortened, the thermal efficiency can be improved, and the productivity can be improved and the operating cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a metal melting furnace to which the present invention is applied.

FIG. 2 is a diagram showing a typical dissolution pattern when iron scrap is melted only with an oxygen burner.

FIG. 3 is a vertical sectional view showing a second embodiment of a metal melting furnace to which the present invention is applied.

FIG. 4 is a vertical cross-sectional view showing a third embodiment of a metal melting furnace to which the present invention is applied.

5 is a vertical cross-sectional view showing the state of tapping the metal melting furnace shown in FIG.

6 is a vertical cross-sectional view of a main part showing another example of the form of the separation part of the metal melting furnace shown in FIG.

FIG. 7 is a vertical sectional view showing a fourth embodiment of a metal melting furnace to which the present invention is applied.

FIG. 8 is a vertical sectional view showing a fifth embodiment of a metal melting furnace to which the present invention is applied.

9 is a diagram for explaining the flame ejection direction and mounting height of the oxygen burner in the metal melting furnace shown in FIG.

FIG. 10 is a vertical sectional view showing a sixth embodiment of a metal melting furnace to which the present invention is applied.

FIG. 11 is a vertical sectional view showing an embodiment of a metal melting furnace for explaining a second metal melting method of the present invention.

12 is a diagram showing the measurement results of Example 1. FIG.

[Explanation of symbols]

21 ... Oxygen burner, 22 ... Melting part, 23 ... Preheating part, 2
4 ... throttle part, 25 ... molten metal, 26 ... tap opening, 27 ... exhaust port, 28 ... lid, 29 ... metal raw material, 30, 31 ... hypotenuse,
32 ... Insertion hole, 33 ... Secondary combustion oxygen nozzle, 34 ... Molten metal stirring nozzle, 37 ... Separation part, 40 ... Water cooling jacket, 41 ... Eccentric burner, 42 ... Rotation mechanism, 43 ... Forming slag

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 7-203617 (32) Priority date Hei 7 (1995) August 9 (33) Priority claiming country Japan (JP) (31) Priority Claim number Japanese Patent Application No. 7-203619 (32) Priority date No. 7 (1995) August 9 (33) Country of priority claim Japan (JP) (31) Priority claim number Japanese Patent Application No. 7-203624 (32) Priority Nihei 7 (1995) August 9 (33) Priority claiming country Japan (JP) (72) Inventor Kimio Iino 3054-3 Shimokurosawa, Takane-cho, Kitakoma-gun, Yamanashi Nihon Oxygen Co., Ltd. (72) Inventor Kikuchi Yoshiki Yamanashi 3054-3 Shimokurosawa, Takane-cho, Kitakoma-gun Nihon Oxygen Co., Ltd. (72) Inventor Yasuyuki Yamamoto 3054-3 Shimokurosawa, Shimokurosawa, Takane-cho, Kitakoma-gun Yamanashi Prefecture

Claims (15)

[Claims] 1. A melting furnace for melting a metal raw material with a flame of an oxygen burner, wherein a preheating part for preheating the metal raw material is provided above the melting part provided with the oxygen burner, and the melting part and the preheating part are provided. A metal melting furnace characterized in that a narrowed portion having an inner diameter smaller than the inner diameters of the melting portion and the preheating portion is provided therebetween. 2. The metal melting furnace according to claim 1, wherein the cross-sectional area of the preheating portion is in the range of 1.4 to 5 times the cross-sectional area of the narrowed portion. 3. The metal melting furnace according to claim 1, wherein the substantial volume of the preheating section is 0.4 to 3 times the substantial volume of the melting section. 4. The metal melting furnace according to claim 1, wherein the melting part and the preheating part can be separated at or near the throttle part. 5. The separating portion between the melting portion and the preheating portion,
The metal melting furnace according to claim 4, wherein the furnace is made of a carbon-based refractory material. 6. The metal melting furnace according to claim 4, wherein a water cooling jacket is provided in the separation part between the melting part and the preheating part. 7. The upper part of the furnace wall of the melting part is formed with a water cooling jacket, and the angle of the inner wall surface of the water cooling jacket from the upper part of the furnace wall toward the narrowed part is 20 to 60 with respect to the horizontal plane.
2. The metal melting furnace according to claim 1, wherein the oxygen burner is provided so as to penetrate the water cooling jacket while being set in a range of degrees. 8. The flame ejection direction of the oxygen burner is 0.2 times the distance between the center of gravity of the melting portion and the burner mounting portion side on the bottom surface of the melting portion, and the distance between the center of gravity position and the inner wall of the oxygen burner mounting portion side. It is oriented in a circle centered on a point approaching a distance, and the circle has a diameter of 0.6 times the distance between the inner wall of the burner attachment side melted part and the opposite melter inner wall. The metal melting furnace according to claim 1. 9. The mounting height of the oxygen burner is such that the volume of the melting portion below the flame outlet of the oxygen burner is 0.35 to 0.9 times the volume of the entire melting portion. The metal melting furnace according to claim 1, wherein: 10. The metal melting furnace according to claim 1, wherein an eccentric burner is used as the oxygen burner, and the eccentric burner is rotatably provided about a burner axis. 11. The metal melting furnace according to claim 1, wherein an oxygen nozzle for secondary combustion is provided above the melting part. 12. The metal melting furnace according to claim 1, wherein a nozzle for stirring molten metal is provided at the bottom of the melting portion. 13. A metal melting method for melting a metal raw material with a flame of an oxygen burner, wherein a preheating part for preheating the metal raw material is provided above the melting part provided with the oxygen burner, and the melting part and the preheating part are provided. In between, using a metal melting furnace provided with a narrowed portion with an inner diameter smaller than the inner diameter of the melting portion and the preheating portion,
An eccentric burner is used as the oxygen burner, and the eccentric burner is rotated about the burner axis line in accordance with the melting stage of the metal raw material. 14. A metal melting method for melting a metal raw material with a flame of an oxygen burner, wherein a preheating part for preheating the metal raw material is provided above the melting part provided with the oxygen burner, and the melting part and the preheating part are provided. In between, using a metal melting furnace provided with a narrowed portion with an inner diameter smaller than the inner diameter of the melting portion and the preheating portion,
A method of melting a metal, comprising charging a carbonaceous material into a molten slag existing on a bath surface during the melting operation of the metal raw material to form the molten slag. 15. The basicity γ of the molten slag is 0.001T−0.6 ≦ γ ≦ with respect to the molten metal treatment temperature T [° C.].
The method for melting a metal according to claim 14, wherein the method is controlled within a range represented by 0.0025T-1.