JPH06220550A - Treatment of iron scrap containing zn in cupolar - Google Patents

Abstract

PURPOSE:To efficiently melt iron scrap by inductively heating the upper part for charging iron scrap to the b.p. of Zn or above. CONSTITUTION:An induction coil 4 is previously embedded near the lower part of a scrap charging port 3 of the cupola and the upper part for charging the iron scrap 1 is inductively heated to the b.p. of the Zn or above. As a result, the Zn contained in the scrap is evaporated, separated and discharged at the time of melting the iron scrap in the cupola. The accumulation of the Zn in the cupola generated at the time of melting the scrap contg. the Zn is obviated and the interruption of the operation for removing the accumulated Zn in the furnace is obviated, by which the stable operation is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preferentially removing Zn in scrap when melting iron scrap containing Zn in a cupola.

[0002]

2. Description of the Related Art Generally, when a scrap containing Zn is melted in a cupola, since the boiling point of Zn is 907 ° C., the vaporized Zn in the lower part of the cupola furnace (about 1500 ° C.) is At around 500 ℃), the agglomeration occurred again and Zn accumulated inside the cupola. The cupola operation was stopped in a short period of time, and the accumulated Zn was removed after cooling the furnace.

Conventionally, in order to solve the above-mentioned problems when utilizing iron scrap containing Zn as an iron source, JP-A-57-57
-85916, as a pretreatment for melting scrap, the scrap is charged into a rotary kiln and heated by a gas burner to a temperature near the boiling point of Zn.
There is a method of vaporizing and separating and removing, and a method of utilizing the exhaust gas of the melting furnace for heating this scrap.
It is proposed in -50406 publication.

[0004]

However, in the conventional method, the pretreatment is performed outside the melting furnace in order to remove Zn from the scrap, so that the scrap after the treatment is charged into the melting furnace. Due to temperature drop and oxidation,
Heat loss and yield decrease occur. In addition, Japanese Examined Japanese Patent Publication Sho 63-50406
Even when using the exhaust gas from the melting furnace,
For example, complex equipment is needed to hold the scrap in the flue. Also, in this case, since the exhaust gas temperature from the cupola is always constant, only heating at a constant temperature is possible, and a separate heating device (gas burner, induction coil, etc.) is required to control the scrap preheating temperature,
Furthermore, the equipment becomes more complicated.

According to the present invention, when the iron scrap containing Zn is melted in the cupola, only a simple device is attached to the Zn scrap.
An object of the present invention is to propose a method for treating iron scrap containing Zn in a cupola that removes iron and dissolves iron scrap with good yield.

[0006]

According to the present invention, when melting iron scrap with a cupola, the upper part of the scrap that has been charged and deposited is heated to a temperature not lower than the boiling point of Zn by induction heating to produce scrap. A method for treating iron scrap containing Zn in a cupola, characterized in that the contained Zn is vaporized and separated and discharged.

[0007]

In the present invention, the upper part of the scrap charged in the cupola is heated to a temperature higher than the boiling point of Zn by induction heating, so that Zn is vaporized and separated together with the hot air from the lower part of the cupola, and a part of Zn vapor is oxidized. And removed by a dust collector or the like. Therefore, since the scrap charged in the cupola is melted after Zn is vaporized and discharged upward in the upper surface portion, it is possible to prevent accumulation of Zn in the cupola.

Further, since the treatment is carried out directly in the furnace, there is no temperature drop or oxidation, and no heat loss or yield reduction, as compared with the treatment outside the furnace. The scrap containing Zn is, for example, scrap of galvanized steel plate, scrap to which a Zn alloy is attached, and the like. The scrap upper portion as referred to herein is a portion including a surface portion of the scrap loaded and accumulated in the cupola and exposed upward.

The installation position of the induction coil in the present invention is
It is most effective to set the position where the strongest induction heating is performed on the upper surface of the charging scrap. The frequency of the alternating current supplied to the induction coil is generally 50Hz or more without any particular specification.However, if the size of the scrap to be charged is large, it is better to select the low frequency and if the size is small, it is better to select the high frequency. It is efficient if the frequency is optimally selected and heated according to the size of.

According to the method of the present invention, not only Zn but also those containing low boiling point Pb, Cd, etc. can be separated and removed by the same principle. Further, according to the present invention, since the induction coil is used for heating, heating / non-heating can be freely controlled by turning the current ON / OFF or adjusting the intensity, and the heating position can be changed by changing the installation position of the induction coil. It can be set freely.

The present invention will be described below in more detail based on examples.

[0012]

EXAMPLE FIG. 1 schematically shows a cupola having a dissolving capacity of 3 ton / hr. The raw material scrap 1 in the furnace body 2 is charged from the raw material charging hole 3 at appropriate times. An AC power supply 5 is connected to the induction coil 4 via a wire 6. The high frequency power source 5 is of a scale of 1000 Hz and 500 kw.

In order to carry out the present invention, galvanized steel scraps were melted using the cupola, and at that time, 200 kw of electric power was continuously supplied to the induction coil. In addition, in order to compare with the prior art, the above-mentioned cupola was also used to melt the galvanized steel scrap without heating by the induction coil. After continuous operation for 2 weeks, the operation was stopped and the inside of the furnace was examined. As a result, in the case of the comparative example, zinc and lumpy deposits with a high zinc concentration were formed on the inner surface of the furnace wall above the tuyere shown in FIG. However, in another campaign in which induction heating was carried out, even in the continuous operation for 2 weeks, these lump-shaped deposits were not observed.

In the conventional method in which the removal of Zn in the upper portion of the scrap charged into the cupola by induction heating cannot be carried out as in the present invention, Zn is accumulated in the cupola when the scrap containing Zn is melted. However, the operation must be stopped to remove the accumulated Zn, or the use of scrap containing Zn must be avoided.

As another comparative example, a method of performing a pretreatment for removing Zn outside the furnace will be shown. That is, this is a method in which galvanized steel scrap is supplied to a rotary kiln, heated to about 1000 ° C. by a gas burner to evaporate and separate Zn, and then melted and operated in a conventional cupola. The yield of the molten metal obtained by this method is compared with the yield in the above-mentioned embodiment of the present invention, and shown in FIG.

In the case of the present invention, the yield of iron is as high as 94%, whereas in the case of the comparative example, a part of iron oxidized in the rotary kiln is used as a scale at the time of being conveyed and charged into the cupola. The total iron content (total of metallic iron and iron oxide) that has been separated and charged into the cupola has decreased, resulting in a low iron source yield of 85%. Further, in the present invention, Zn
Induction heating is performed only when melting scrap containing smelting, and in other cases, induction heating is not performed.Therefore, electricity is not used as a part of melting energy, but uneconomical due to increased power costs. It does not dissolve easily.

[0017]

In the present invention, since Zn is vaporized and removed from the upper portion of the charging scrap in the cupola by induction heating, the Zn in the cupola generated when the scrap containing Zn is melted by the conventional method is dissolved. It has become possible to eliminate the accumulation of. Therefore Zn accumulated in the furnace
Therefore, stable operation can be performed even when scrap containing Zn is used for removing the above without interrupting the operation.

Further, in the present invention, since Zn can be efficiently discharged out of the system, it is possible to recover and reuse Zn or Zn oxide by installing a Zn coagulation facility in a part of the exhaust gas treatment system of cupola. , It also has an advantage that Zn resources can be effectively used.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an outline of a cupola used in the present invention.

FIG. 2 is a diagram comparing the molten metal yields of the present invention and a comparative example.

[Explanation of symbols]

 1 Raw Material Scrap 2 Furnace Main Body 3 Raw Material Input Hole 4 Induction Coil 5 High Frequency Power Supply 6 Wiring 7 Hot Water Hole 8 Blower Pipe

Claims (1)

[Claims] 1. When melting iron scrap in a cupola, the upper part of the charged and deposited scrap is heated to a temperature not lower than the boiling point of Zn by induction heating to vaporize and separate Zn contained in the scrap. A method of treating iron scrap containing Zn in a cupola, characterized by discharging.