JPH09184005A - Method for charging scrap into shaft melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the filling ratio scrap to be filled by charging a prescribed size of the scrap into a part having gas temp. on the charged surface higher by a specific temp. than a reference value. SOLUTION: In order to beforehand inform an operator of the gas temp. pattern on the charged surface 4 at the time of executing the normal operation, the gas temp. on the charged surface 4 is continuously measured with one or more of sondes 3 arranged near the upper part of the charged surface 4 and the measured value is made as a reference value in each point. When the scrap is unevenly mixed and charged, gap is developed near the upper part of the charge surface 4. At this time, since the gas flowing speed at this part becomes high and the heat conduction to the scrap is not executed in good condition, as a result, the gas temp. on the charged surface 4 becomes high, and development of the gap can be detected by measuring this gas temp. Since the gap at this part can be filled by charging the prescribed size of scrap to the part having higher gas temp. than the reference value, the filling ratio of the scrap in the furnace becomes constant.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing molten iron by melting scrap such as pig iron or steel scrap in a shaft melting furnace, and adjusting the scrap charging method from the furnace top to stabilize the molten iron. The present invention relates to a scrap charging method for a shaft melting furnace that produces efficiently.

[0002]

2. Description of the Related Art A method for producing molten iron from scrap is
The cupola melting furnace method, which is a conventional shaft furnace, is widely used. In other words, charging scrap and coke,
By blowing hot air from the bottom of the furnace, scrap is melted to produce molten iron. Here, in order to ensure air permeability in the furnace, the grain sizes of scrap and coke are sufficiently adjusted to achieve stable operation. The conventional cupola melting furnace has a relatively small diameter of 2 to 3 m and the length of scrap to be charged is approximately 50 to 200 mm (normal scrap).
Therefore, the filling rate of the shaft melting furnace was almost uniform, and the fluctuation of the operating conditions for scrap melting was small.

[0003]

However, recently, with the increase in the amount of scrap, a melting furnace having a diameter of more than 4 m has come to be used. In this case, the supply amount is not enough with ordinary scrap alone, and the scrap length is 1
It has become necessary to use large scraps of around 000 mm. If this large scrap is used, the scrap filling rate in the melting furnace tends to be non-uniform, heat transfer to the scrap fluctuates, and there is a problem that the operation is not stable. Further, in order to adjust the grain size of scrap, it is sufficient to cut and adjust a large scrap, but there is a problem that this leads to an increase in manufacturing cost.

As a method for solving the above problems,
In Japanese Patent Laid-Open No. 60-103291, a large-sized scrap is put into the center of the furnace using a guide chute at the top of the furnace, and then a fine scrap such as a shredder is put into the wall of the furnace. , A method of controlling gas flow is disclosed.

However, in this method, actions that can be taken regarding the raw material charging method are disclosed even if the conditions for heat transfer to scraps change due to changes in the charging conditions and the size of the charging raw material. However, there was still a problem that the molten iron temperature fluctuated and the furnace condition became unstable.

The present invention has been made in order to solve the above-mentioned problems, and makes it possible to make the scrap filling rate in the furnace uniform and to stably melt the scrap. It provides a method.

[0007]

The scrap charging method for a shaft melting furnace of the present invention is a scrap charging method for a shaft melting furnace in which scrap is charged from above, and one or more locations near the furnace top charging surface are provided. The gas temperature at each position was continuously measured, and it was judged as an abnormal value when the gas temperature at each position became higher than the gas temperature on the charging surface under normal conditions by an abnormal value, and this abnormal value was shown. It is characterized in that a predetermined length of scrap is charged on the charging surface.

According to a second aspect of the present invention, in the scrap charging method according to the first aspect, 1 is provided on the charging surface showing an abnormal value.
It is characterized in that scrap having a length of 00 mm or less is charged.

Here, the scrap length (L) is as shown in FIG.
It means the maximum length of scrap as shown in. In this figure, (a) shows the length of ordinary scrap or small scrap, and (b) shows the length of large scrap such as H-section steel.

In order to know the gas temperature pattern on the charging surface during normal operation in advance, it is arranged near the charging surface 1
The gas temperature on the charging surface is continuously measured with more than one sonde, and this is used as the reference value at each point.

FIG. 6 is a schematic diagram showing the relationship between the scrap temperature and the gas temperature in the vicinity of the charging surface of the furnace top.
The gas temperature on the charging surface was represented by the gas temperature in the east and west of the melting furnace. In the figure, squares are large scraps, ○ are ordinary scraps, and ● are small scraps. (A) is a diagram during normal operation in which large scraps and ordinary scraps are uniformly mixed, and (b) is a mixture of large scraps and ordinary scraps on the charging surface of the furnace top. FIG. 6C is a diagram when the scraps are uniformly mixed, and FIG. 7C is a diagram when the scraps are charged by the charging method of the present invention from the scrap accumulation state of FIG.

When a void is formed near the charging surface of the furnace top (east side of FIG. 6 (b)), the flow velocity of the gas in the portion where the void is generated becomes high, and heat transfer with scrap is not performed well. Since the gas temperature on the charging surface becomes high, the generation of voids in the furnace can be detected by measuring the change in gas temperature on the charging surface. By charging a scrap of a predetermined size in a portion where the gas temperature is higher than the reference gas temperature by a predetermined temperature, the void in that portion is filled, so that the filling rate in the furnace becomes constant.

As is apparent from the schematic diagram of FIG. 6 (c), a small scrap is initially charged in a portion where the gas temperature becomes high, and then a mixture of large scrap and ordinary scrap is charged, so that the furnace is used. The gas temperature near the top charging surface becomes uniform.

Although the predetermined temperature differs depending on the size of the melting furnace and the operating conditions, it is higher than the reference value by 20 to 80 ° C., and usually it is preferably set to about 50 ° C.

Further, it is appropriate that the length of scraps charged in the portion where the gas temperature on the charging surface becomes high is 100 mm or less, preferably 50 to 100 mm.

If the length of scrap exceeds 100 mm, it is too long to fill the voids. In addition, a moveable armor is used to adjust the charging position of the charged material at the furnace top, but if the scrap length exceeds 100 mm, the moveable armor may be damaged.

If the length of the scrap is 50 mm or less, the scrap is too small to fill the void portion too much, and the filling rate of the portion becomes too large, so that the filling rate in the cross-sectional direction in the furnace becomes uneven.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of a shaft melting furnace according to an embodiment of the present invention, (a) is a vertical sectional view, and (b) is an XX sectional view of (a). 1 is a shaft melting furnace, 2
Is a scrap charging port, 3 is a sonde, 4 is a charging surface, 5 is a movable armor, 6 is a blower for a shaft melting furnace, and 7 is
Is a tap of the shaft melting furnace, and 8 is a measuring terminal for measuring temperature.

The melting amount of the shaft melting furnace 1 is 3000 t /
The shaft melting furnace 1 has a diameter of 4.5 m and a height of 10
m. Raw materials such as scrap, coke and limestone are fed from the scrap charging port 2 in the shaft melting furnace 1 to the charging surface 4
It is charged in batch form.

High-temperature air is blown from the blower opening 6 to burn the coke in the furnace and generate high-temperature gas. The charged material descends in the furnace as the coke burns, the scrap heated during this is melted, the molten iron is collected at the furnace bottom, and tapped from the tap hole 7.

The movable armor 5 is a device for charging scrap at an arbitrary position on the charging surface of the furnace top.

Above the shaft melting furnace 1, a sonde 3 for measuring the gas temperature of the scrap charging surface is installed.
The measuring terminal 8 is embedded in the sonde 3, and the gas temperature on the charging surface at the five positions in the radial direction of the melting furnace can be measured.
In this embodiment, two sondes 3 are installed at right angles.

The number of sondes 3 installed depends on the conditions of operation and equipment. The operation of the sonde 3 is that when the scrap is charged, the sonde 3 may be damaged by the impact of dropping the scrap, so the sonde 3 is pulled out of the system of the shaft melting furnace 1, and after the scrap is charged, the shaft melting furnace 1 It is designed to be inserted inside.

[0025]

EXAMPLES Table 1 shows the shapes of scraps used in Examples of the present invention.

[0026]

[Table 1]

The shape of the scrap is usually a machined cutting scrap, and the length of the scrap is 50 to 200 mm. The large-scale scrap is construction steel cutting waste, and the length of the scrap is 1000 to 2000 mm. Small scraps are steel scraps smaller than ordinary scraps, and the length of scraps is 50 to 100 mm.

FIG. 2 shows that 70% by weight of ordinary scrap,
It is a figure which shows the time-dependent change of the gas temperature on the charging surface at the time of normal, when what mixed large-scale scrap with 30 weight% was charged from the furnace top with a large bucket.

In this figure, 500 m from the center of the furnace and the furnace wall
The gas temperature is shown for each of the inside of m and for a total of 3 points. The scrap charging interval from the furnace top is 15 minutes, and the charging amount is 30 tons.

∇ in FIG. 2 indicates the time when scrap is charged. The gas temperature on the charging surface changes periodically because scrap is batch-charged.

The gas temperature rises approximately 5 minutes after the scrap is charged, and then becomes almost constant, and there is almost no change thereafter.

Although the gas temperature on the furnace wall side is lower than the furnace center,
This is due to heat dissipation from the furnace wall. The reference pattern is the change over time in the gas temperature on the charging surface at each position in this figure.

The reference gas temperature under the operating conditions at this time was about 220 ° C. in the center of the furnace and about 150 ° C. in the east and west.

The molten iron temperature at this time is 1505 ° C.,
The amount of molten iron dissolved was 125 T / H.

FIG. 3 shows changes with time in the gas temperature on the charging surface when the furnace condition changes when charging a mixture of 70% by weight of normal scrap and 30% by weight of large scrap. is there.

As is apparent from this figure, the gas temperature on the charging surface on the furnace wall side (east side) became about 100 ° C. higher than the normal temperature after a certain time passed after the scrap charging. When such an operation was continued, the temperature of the molten iron dropped by about 30 ° C.

The molten iron temperature at this time is 1475 ° C.,
The amount of molten iron dissolved was 125 T / H.

At this time, since the predetermined temperature difference was set to 20 degrees, it was judged to be abnormal. This is because the gap in the cross-sectional direction on the furnace wall side (east side) became large and gas blow-through occurred.

Therefore, 3.0 t of small scrap was initially charged at the position where the gas temperature was high on the furnace wall side (east side). After that, 70% by weight of ordinary scrap and 3 of large scrap
A mixture of 0% by weight and 27 t was charged.

For charging the small scrap, a movable armor generally used in a blast furnace for controlling the charging and dropping position of the charging surface was used.

FIG. 4 shows the changes over time in the gas temperature on the charging surface during this operation. In FIG. 4, ▼ is the time when a small scrap is loaded, and ▽ is the time when a mixture of ordinary scrap and large scrap is loaded. As is clear from this figure, the temperature difference between the measurement positions returned to the original state by charging the small scrap three times in the portion where the gas temperature was high. This is because charging the fine scrap in the high temperature portion increased the filling rate, resulting in a uniform gas flow in the furnace.

The molten iron temperature was 1505 ° C., the molten iron dissolved amount was 125 T / H, and the molten iron temperature quickly recovered to the original temperature.

[0043]

EFFECTS OF THE INVENTION According to the present invention, 1 near the charging surface of the furnace top
Continuously measuring the gas temperature at more than one position, and when the gas temperature at each position becomes higher than the gas temperature on the charging surface at the time of normal by a predetermined temperature, the charging surface shows an abnormal value. Since the filling rate of the scrap charged into the furnace with a predetermined length of scrap charged therein can be made uniform, the melting of the scrap is stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a scrap melting furnace according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a gas temperature on a charging surface and a scrap charging time in a normal state.

FIG. 3 is a diagram showing a relationship between a gas temperature on a charging surface and a scrap charging time when a change occurs in a furnace condition.

FIG. 4 is a diagram showing the relationship between the time variation of the gas temperature on the charging surface and the scrap charging time after taking an action for operation after the change in the furnace condition has occurred.

[Fig. 5] Time-dependent change of gas temperature on the charging surface and scrap in the present embodiment under normal conditions, when changes occur in furnace conditions, and when operational actions are taken after changes occur in furnace conditions It is a figure which shows the relationship with charging time.

FIG. 6 is a schematic diagram showing a relationship between a gas accumulation temperature and a scrap accumulation state in the vicinity of a charging surface of a furnace top.

[Explanation of symbols]

 1 Shaft melting furnace 2 Scrap charging port 3 Sonde 4 Charged surface 5 Movable armor 6 Blower port 7 Molten iron port 8 Measuring terminal

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takanori Inoguchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Inventor Ryota Murai 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Date Main Steel Pipe Co., Ltd.

Claims (2)

[Claims] 1. In a scrap charging method for a shaft melting furnace in which scrap is charged from above, gas temperatures at one or more positions in the vicinity of the furnace top charging surface are continuously measured, and the temperature at each position is measured. An abnormal value is set when the gas temperature is higher than the gas temperature on the charging surface under normal conditions by a predetermined temperature, and a predetermined length of scrap is charged on the charging surface showing the abnormal value. Scrap charging method for shaft melting furnace. 2. 100 m on the charging surface showing an abnormal value
The method for charging scrap in a shaft melting furnace according to claim 1, wherein scrap having a length of m or less is charged.