JPH0978117A - Operation of converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the erosion of a refractory lined in a converter by estimating heat load applied on the refractory during operation from a temp. measurement to a furnace outer iron shell and a remaining thickness of the refractory to use the setting of a good operational condition at the next time. SOLUTION: A thermometer 5 is set to an arbitrary position in the iron shell 3 surrounding the outer periphery of the converter 1 and the thickness Li (m) of the refractory 4 in the furnace near the temp. measuring part of the iron shell 3 is measured immediately after tapping molten steel. The local heat load Qi (kcal/m<2> .hr. deg.C) applied to each position during operation is measured based on this thickness Li and the iron shell temp. Ti ( deg.C) with the thermometer 5 and the operational condition in the following time is set so that the local heat load Qi in each position uniformizes. Further, the local heat load Qi is calculated with the equation Qi=K/Li×(Ti2-Ti1). Wherein, Ti2 is the surface temp. of the refractory in the furnace ( deg.C) and K is the thermal conductivity of the refractory (kcal/m.hr. deg.C). By this method, the erosion speed of the lining refractory 4 is made to slow and the erosion in the whole periphery of the furnace is uniformly progressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a converter, and more specifically, for suppressing melting loss of a refractory lined in a converter,
The present invention relates to a converter operating method for estimating the heat load applied to the refractory during operation from the temperature measurement of the furnace outer shell and the remaining thickness of the refractory, which is useful for setting the next operating condition.

[0002]

2. Description of the Related Art Since the life of the furnace body of a converter has a great influence on the cost of steelmaking, there have been many development studies on the extension of the life of the furnace body. Perhaps because of this, despite the recent expansion of furnace volume and severer operating conditions, the same furnace cost 10
Converters that can achieve over 000 charges have also appeared. It can be said that this is a comprehensive result of the remarkable development of furnace construction, repair or operation technology along with the improvement of refractory quality.

By the way, among these techniques for extending the life of the furnace body, the protection management of the lining refractory during operation is also important, and conventionally, the technique for knowing the thickness of the lining refractory of the converter in use is known. Is being studied. For example, JP-A-48-80
Japanese Patent No. 406 discloses a method of arranging a plurality of thermometer contacts on the outer peripheral surface of the iron shell to measure the iron shell temperature and estimating the thickness of the refractory in the furnace using the measured values. Further, regarding the technique for measuring the remaining thickness of the refractory lined in the converter, for example,
(Corporation) "Iron and Steel" issued by Japan Iron and Steel Institute, vol. 80,
A laser brick residual thickness measuring device has also been developed as described in "Improvement of Converter Refractory Residual Thickness Management Method" reported by Kakogawa Works of Kobe Steel, Ltd. at T162 (1994).

However, the above-mentioned JP-A-48-8040
The technique described in Japanese Patent Publication No. 6 only estimates the remaining thickness of the bricks lined in the converter, thereby effectively using the bricks up to a thickness that is safe for operation and helping to extend the life of the furnace body. You can estimate the time of body repair and the time of furnace shutdown,
Although local wear can be found promptly, these effects are merely secondary and do not provide a method for specifically suppressing the wear of bricks in one furnace cost. Further, even with the laser-type refractory residual thickness measuring device, the same effect as described above can be achieved with high accuracy only by measuring the brick residual thickness. In other words, in the existing iron skin temperature measurement and brick residual thickness measurement and estimation, each measured value is used only for the management of refractories, and the goodwill protection measures directly linked to the operating conditions of the converter The current situation is that it has not arrived.

[0005]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention effectively utilizes the existing measuring technology in a converter to achieve a slow erosion rate of the refractory lining and a uniform furnace circumference. It is an object of the present invention to provide a converter operating method that promotes melting loss.

[0006]

In order to achieve the above-mentioned object, the inventor can obtain the measured temperature of the refractory lining by refracting the lining refractory of the furnace from the data measured by the existing technique. I thought that the thickness of the material could be used together. because,
Even if the measured values of the iron shell temperature and the refractory thickness are individually referred to for the next operation condition setting, if only that, for example, when the residual refractory is thick and the heat load is large, the melting loss will be significant in the future operation. Because it is expected and not enough. Moreover, since the heat load reflects the refractory state at the present time, if it is obtained at each place and treated so as to be the same as possible, the shape of the furnace does not become peculiar and the melting rate The present invention was devised on the assumption that

That is, the present invention is a converter operating method in which oxygen is blown from the upper blowing lance to the molten iron surface held in the furnace while measuring the iron shell temperature at a plurality of locations on the outer periphery of the furnace body, immediately after tapping. The thickness of the refractory in the furnace near the temperature measuring part of the iron skin is measured, and the local heat load applied to each part during operation is estimated by the temperature measurement value and the thickness, and the local heat load of each part is uniform. The converter operating method is characterized by setting the next operating condition so that The present invention is also a converter operating method characterized by estimating the above-mentioned local heat load by the following formula.

Qi = K / Li × (Ti 2 −Ti 1) (1) where Qi: Local heat load (kcal / m ² · hr)
・ ° C) Ti1: iron shell temperature (° C) Ti2: surface temperature of refractory in furnace (° C) Li: refractory thickness measurement value (m) K: thermal conductivity of refractory (kcal / m · hr ・
° C).

Further, the present invention is characterized in that the temperature measuring portion of the iron skin is three or more, and the operating conditions are as follows: the discharge hole position of the upper blowing lance, the discharge hole number, the discharge hole angle,
The converter operating method is characterized in that it is one or more selected from the lance height and the flow rate of the discharged refining gas. By operating using these inventions, it is possible to effectively utilize the measurement technology in the existing converter, to slow down the erosion rate of the refractory lining, and to promote the erosion uniformly over the entire circumference of the furnace. become.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, a method of estimating a local heat load, which is a key point of a converter operating method according to the present invention, will be described with reference to FIG. A thermometer 5 is installed at an arbitrary portion of the iron shell 3 surrounding the outer periphery of the converter 1, and the measured value of the thermometer 5 is Ti1 (° C.),
The temperature of the surface of the refractory 4 lined inside the furnace at the site where the thermometer is installed is Ti2 (° C), the residual thickness of the refractory measured after each blowing is Li (m), and the thermal conductivity of the refractory is K (kca
1 / m · hr · ° C). Here, during the converter operation or near the end of tapping, the temperature distribution related to the refractory cross section is considered to be a pseudo steady state. So-called local heat load Qi
(Kcal / m ² · hr · ° C) can be expressed by the following formula.

Qi = K / Li × (Ti 2 −Ti 1) (1) In the formula (1), the temperature Ti 2 (° C.) of the refractory surface is almost equal to the atmosphere temperature in the furnace and the steel bath temperature. In the invention, the steel bath temperature at the end of the operation is selected as a representative value.
Therefore, by substituting the measured values Ti1 and Li into the equation (1), the magnitude of the local heat load Qi can be calculated at a predetermined portion.

In the present invention, a large number of local heat loads are obtained on the outer circumference of the converter (for example, in FIG. 2, Ti1, Tj1, and T11 are obtained as iron skin temperature measurement values at three points, i, j, and l positions). Further, by obtaining the brick residual thickness of the temperature measurement portion as Li, Lj, and L1 immediately after tapping, local heat loads Qi, Qj, and Ql on refractories at the same height of the converter can be known. . On the other hand, for example, two points in the height direction of the same converter,
Here, by obtaining T1ml and Tnl at the positions of m and n as iron skin temperature measurement values and the brick residual thickness near the temperature measurement site as Lm and Ln, the refractory in the height direction of the converter is obtained. The local heat loads Qm and Qn will be known.

In the present invention, the sizes of Qi, Qj, Q1 in the circumferential direction at the same height or the sizes of Qm, Qn at different heights are respectively compared, and the difference in these heat loads is compared. The next blowing condition should be set so that the above will not occur as much as possible. On the other hand, as a method for changing the local heat load, the position of the secondary combustion (combusting CO gas generated on the steel bath surface by oxygen blowing) region in the furnace is changed, specifically, Changing the height of the top blowing lance 2 for supplying oxygen as a refining gas, changing the acid transfer rate, changing the size of the discharge hole to improve the discharge rate of oxygen from the lance, There is a method of replacing the lance with a different number of discharge holes. As a method of changing the local heat load in the circumferential direction of the same height, the positions of the discharge holes of the upper blowing lance may be unevenly distributed in the circumferential direction, or the number of discharge holes may be unevenly distributed in the circumferential direction. Alternatively, a method may be considered in which the diameters of the discharge holes are replaced with lances that are non-uniformly distributed in the circumferential direction.

[0014]

EXAMPLE 160 tons / ch of hot metal was charged into an upper-bottom blow converter type reactor vessel capable of smelting reduction of Cr ore in an iron bath, and a large number of crude stainless steel melts were melted by smelting reduction. In either case, the supply flow rate of top blowing oxygen is 900 Nm.
³ / min, the feed rate to 1.4 t / min of Cr ores, the reduction carbon material was continuously charged from the furnace 1.7 t / min lump coke. The top blowing lance has a 35 mmφ discharge hole.
The one having 0 holes was used as a basic form. As the bottom blowing stirring gas, a mixed gas of oxygen and nitrogen was caused to flow at a constant flow rate of 90 Nm ³ / min.

Here, during oxygen blowing, i1, shown in FIG.
JIS on the iron skin at the position of j1, 11, i2, j2, 12
A K-type SUS-coated thermocouple was welded to the iron shell, and the iron shell temperature was continuously measured. Then, using a laser type refractory residual thickness measuring device, the refractory residual thickness of the portion corresponding to the above symbol portion is measured within 10 minutes after tapping of each charge, and Li1, Lj are measured.
The values were 1, L11, Li2, Lj2, and L12. The local heat load of each part was calculated by the equation (1), and Qi
1, Qj1, Q11, Qi2, Qj2, Q12.

(Invention-1) When the above-mentioned temperature and residual thickness were measured after 400 charges from the start of use in the container lined with a new refractory, Qj1 was 2530.
0kcal / m ² · hr and other values 18900kca
It was found that it was larger than 1 / m ² · hr, and the discharge hole diameter of the upper blowing lance was changed from 35 mmφ to 20 mm so as to reduce the oxygen supply amount at the relevant part of Qj1 from the next blowing of the charge.
Reduced to φ. At the time of reduction, in order to avoid the complexity of lance replacement, a pipe having an inner diameter of 20 mmφ and an outer diameter of 35 mmφ was inserted into the discharge hole.

(Invention-2) While continuing the measurement, Qi was measured at 400 charges after the implementation of Invention-1.
2, Qj2, Q12 is 34000-36000 kcal
/ M ² · hr, other 18,000 to 20,000
It was found to be larger than kcal / m ² · hr.
Therefore, from the next charge, the height of the top blowing lance is set to 3.
It was changed from 2m to 4.5m, and blowing was performed at a higher position than before.

(Invention-3) Furthermore, when the measurement was continued and the operation was continued, 400 after the implementation of Invention-2.
Qj1 is 26,500 kcal / m ² hr on charge
And values at other parts 22,000 kcal / m ² hr
It was found that it was larger than that of No. 1, and the upper blowing lance without the discharge hole was used so that the oxygen supply amount of the relevant portion of Qj1 would decrease from the next blowing of the charge. In implementing this, in order to avoid the complexity of lance replacement, a copper round bar was inserted into the conventional discharge hole.

(Invention-4) The operation was started again in the container lined with a new refractory material, and the temperature and the residual thickness were measured after 400 charges from the start of its use.
1, Qj1 and Q11 are 28,000 kcal / m ² hr
In both cases, the value of other parts is 18,000 to 20,000.
It was found to be larger than 0 kcal / m ² hr. Therefore, from the next charge, the discharge hole angle (angle from the vertical line) 12 ° of the upper blowing lance was changed to 24 °. The change was made by replacing it with another lance having such a discharge hole angle.

(Invention-5) The present invention-4 was operated while continuing measurement, and Q was measured at the 400th charge.
i2, Qj2 and Q12 are 30,000 to 32,000k
Cal / m ² hr and other values of 21,000-2
It was found to be larger than 1,500 kcal / m ² hr, and the oxygen supply amount from the upper blowing lance was 600 Nm ³ / in order to increase the oxygen supply amount from the next charge blowing.
It was increased from min to 850 Nm ³ / min.

(Comparative Example) On the other hand, in another container lined with a new refractory, when the above measurement was started after the 400th charge of blowing, Qi1 and Qj1 were 25000k.
Other values of 17,000 kcal / cal / m ² · hr
It was found to be larger than m ² · hr, but continued blowing after the next charge without changing operating conditions.

The above operation results are summarized in Table 1. The evaluation was performed by measuring the refractory thickness corresponding to the positions of i1, j1, 11, i2, j2, and 12 and the refractory thickness corresponding to the intermediate position of each position, with a total charge of 300 after application of the present invention. The average erosion rate (mm / charge) of the refractory was measured according to whether the distribution was almost uniform. In the comparative example, the distribution of the average erosion rate (mm / charge) at a total of 800 charges was evaluated. The results are collectively shown in Table 1.

[0023]

[Table 1]

As is clear from Table 1, the present invention-1,
In 2, 3, 4 and 5, after applying the present invention, 3 respectively.
The average erosion rate after the 00 charge was 0.4 mm / charge, and uniform wear could be achieved in the furnace. The furnace in which the present invention has been attempted has been adapted to the present invention while further comparing the distributions of local heat loads thereafter, and has achieved a total furnace life of 1800 charges. On the other hand, in the comparative example, the average wear rate near the site where the local heat load was large was 0.7 to 1.0.
mm / charge and its size were about twice as large as the surrounding area, and even when the inside of the furnace was observed, it deteriorated to the extent that a dent was visually recognized. In the comparative example, the remaining thickness of this worn part disappeared at the 900th charge and the permanent brick was exposed, so the repair of the furnace was started.

[0025]

As described above, according to the present invention, since the heat load distribution in the furnace is made uniform at each place in the furnace, the wear of the refractory lining the converter can be made uniform, and the refractory body It was possible to use the refractory evenly and safely to the maximum thickness without causing local erosion, and it was possible to greatly reduce the amounts of refractory and mixed gas used.

Further, since the heat load can be applied uniformly, the temperature of the iron shell also has a uniform temperature distribution, and it can be operated in a healthy state without causing abnormal deformation as in the case of local heating. There was also an effect that the life of the converter iron shell can be greatly improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a temperature measurement portion of a converter operating method according to the present invention.

FIG. 2 is another example showing a temperature measurement portion in the converter operating method according to the present invention.

FIG. 3 is a diagram showing an embodiment of a converter operating method according to the present invention.

[Explanation of symbols]

 1 Converter 2 Top blowing lance 3 Iron skin 4 Refractory lined in the furnace 5 Thermometer 6 Slag 7 Molten steel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Kuroki 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Chiba Works (72) Inventor Atsushi Kiriya 1 Kawasaki-cho, Chuo-ku Chiba Steel Co., Ltd. Chiba Steel Co., Ltd. In-house

Claims (4)

[Claims] 1. A converter operating method in which oxygen is blown from a top blowing lance to a molten iron surface held in the furnace while measuring the temperature of the iron shell at a plurality of locations on the outer periphery of the furnace body. Measure the thickness of the refractory in the furnace near the temperature measuring unit, estimate the local heat load applied to each part during operation with the temperature measurement value and the thickness, next time to make the local heat load of each part uniform A converter operating method, characterized in that the operating conditions are set. 2. The converter operating method according to claim 1, wherein the local heat load is estimated by the following equation. Qi = K / Li * (Ti2-Ti1) (1) where Qi: Local heat load (kcal / m ² · hr)
・ ° C) Ti1: iron shell temperature (° C) Ti2: surface temperature of refractory in furnace (° C) Li: refractory thickness measurement value (m) K: thermal conductivity of refractory (kcal / m ・ hr ・
° C). 3. The converter operating method according to claim 1 or 2, wherein the temperature measuring portion of the iron skin is three or more. 4. The operating condition is one or more selected from the discharge hole position of the upper blowing lance, the discharge hole number, the discharge hole angle, the lance height and the flow rate of the discharged refining gas. The converter operating method according to any one of 1 to 3.