JPS6216244B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a device that shortens the replacement time when switching the bottom blowing gas in a converter and controls fluctuations in pressure in front of the tuyere to extend the life of the tuyere. In general, a bottom-blown converter is operated by changing the type and amount of blown gas according to the operating conditions at each stage, such as charging, blowing, sedation, tapping, slag, and suspension. , the state is illustrated by the conceptual diagram of FIG. In FIG. 1, 1 is a converter, 2 is molten steel, 3 is a tuyere, and 4 is a trunnion core. The switching operation is first performed based on the gas switching command 5, the status command 6, and the tilting angle command 7, and the switching operation is performed using the gas switching command 5, the status command 6, and the tilting angle command 7 as starting points. , check valve 12,
12', the process is completed by replacing the leading gas G1 in the pipe 13 between the shutoff valves 10, 10' and the tuyere 3 with the trailing gas G2. The time required to complete the replacement varies depending on the equipment layout and operating conditions of the converter, but is approximately 20 ^sec to 120 ^sec . On the other hand, the converter 1 is tilted, for example, in the direction of the arrow F, and the relative position between the surface edge point A of the molten steel 2 and the tuyere 3 changes.
The time t (sec) required for the surface of the molten steel to cross the point B at the extreme end of the tuyere 3, that is, until the tuyere 3 begins to be exposed from the molten steel 2 due to the inclination of the converter 1, is the time t (sec) required for the tuyere to begin to be exposed. Tilt angle θ and tilt speed υ up to
(rpm), but normally the tilting speed υ is
The speed is 1.0 to 2.0 rpm, and the required time t is 20 ^seconds or less. In Fig. 1, 15, 15' are flowmeters, 1
6 and 16' are original pressure gauges, and 17 is a tuyere front pressure gauge. As mentioned above, since it takes about 20 to 120 ^seconds to replace the leading gas G1 and the trailing gas G2, the converter 1 is already in a tilted position, and the tuyeres 3 at the bottom of the furnace are exposed to the molten steel 2.
Even if it is exposed further upward, gas replacement is still occurring and the preceding gas G1 is being blown into the furnace. Therefore, gas that should not be blown in at the end of the tilting movement is blown in, which affects the tuyere 3 as shown in Table 1 and causes tuyere trouble. As an example, we will explain the case where the refining stage progresses to collapse/sedation, or the steel tapping stage begins. During the refining period, the O ₂ injected from the inner pipe is not completely replaced with the trailing gas until the furnace is overturned, exposing the tuyere 3, and when it exits the molten steel 2, it melts the pine room of the tuyere protective layer. Lose. In addition, since the heat load is large in the outer tube during the refining stage, strong cooling gas is injected into the outer tube, but when the tuyere is exposed outside the molten steel 2 due to the tilting of the furnace, the tuyere is damaged due to rapid supercooling. cracks occur. In addition, due to the long replacement time of gas species, [O] [N] [H] [C] in steel as shown in Table 1
Steel quality is affected by changes in the composition of steel, changes in temperature, etc.

[Table] There are two gas switching methods: a flow rate confirmation method and a valve opening confirmation method. In either case, for the first few seconds at the time of switching, the flow rate of the trailing gas is lower than that of the leading gas. This will add to the pressure and increase the pressure inside the pipe. To suppress this pressure increase,
It is possible to increase the piping capacity, but this will make the replacement time described earlier longer, and no matter which gas switching method is used, such as pressure control, flow rate control, or specified valve opening, the pressure inside the converter will increase, causing the It is not practical because it increases the mouth pressure and causes pine room scattering, tuyere brick cracks, etc. The purpose of the present invention is to provide a bottom-blown gas switching device that can solve these problems and prevent tuyere troubles and changes in steel quality, and its gist is as follows: The capacity of the piping from the shutoff valve closest to the tuyere to the tuyere is the amount required to tilt the converter body from an upright position to a tilted position where the tuyere begins to be exposed above the molten steel surface. This is a bottom-blown gas switching device in which the cutoff valve is disposed at a position where the capacity reaches a capacity where gas switching and replacement is completed within time t, and a two-stage controlled dispersion device is provided in the piping. The details are described below. First, the time t required for the tuyere 3 to be exposed above the molten steel 2 as the converter 1 tilts depends on the structural conditions determined by the plan of the converter equipment, the furnace body tilting speed, etc. Although it is determined by the operating conditions, this is determined in advance as a unique condition for each converter. Therefore, in the present invention, in order to complete the injection of the preceding gas remaining in the pipe connected to the tuyere into the furnace within the required time t at the time of switching,
The size of the capacity V of the piping from the shutoff valve 10 provided in the piping at a position immediately adjacent to the tuyere to the tuyere 3 was limited. That is, the piping capacity V from the shutoff valve to the tuyere
is made sufficiently small, the amount of lead gas remaining in the piping section is reduced by shutting it off with the shutoff valve, and the remaining lead gas is discharged into the converter within the required time t. made possible. In the device of the present invention, the shutoff valve 1 located close to the tuyere
0 as close as possible to the tuyere 3. Specifically, at the design stage, the gas flow rate Q and
In the relationship between the pipe capacity V and the gas pressure P in the pipe, the balance with the required time t is t>PV/Q
Determine the position of the shutoff valve so that it is, and arrange it accordingly. However, even if the balance between the piping capacity V and the required time t satisfies the conditions, the pressure of the leading gas and the trailing gas will rise due to the pressure addition phenomenon during a very limited time period, and the tuyeres will be damaged. It cannot be avoided that there is a risk of In the present invention, this pressure increase is eliminated by a two-stage relief valve. For example, discharging valves 14, 14' are provided between the tuyere and the shutoff valve shown in FIG. The reason why two of these relief valves are provided is to adjust the pressure in front of the tuyeres in stages as shown in FIG. That is, in the valve opening confirmation switching method in the column, when the leading gas G1 satisfies the maintenance of the specified opening and flow rate by the transition command, the shutoff valve 10' of the trailing gas pipe opens and the trailing gas _G2 switches to the pipe 1.
After it is confirmed by the flow meter 15' and the source pressure gauge 16' that the predetermined opening degree and source pressure for securing the flow rate are secured, the preceding gas cutoff valve 10 is closed. If there is no release valve, the pressure inside the pipe 13 (indicated by the pressure gauge 17 in front of the tuyere) during this period will rise step by step as the trailing gas G ₂ is superimposed on the leading gas G ₁ and then drop, as shown in . . In order to prevent pressure fluctuations as shown in FIG. By closing 14' and also closing the relief valve 14 at point , the pressure changes as shown by , and a rise in pressure can be prevented. Regarding the flow rate confirmation method in the column, check the specified flow rate value for trailing gas G ₂ and then close the shutoff valve 10 for leading gas G ₁ .
Since it is closed, the same phenomenon as the method occurs. In the illustrated example, two diffusion valves are installed, but as shown in Fig. 5, it is also possible to perform control with one diffusion valve 14''. A regulating valve or orifice 18 is installed below the dispersion valve 14'' to eliminate the pressure groove when dissipating all at once, but in any case, it is necessary to use a dispersion device that controls the discharge in two stages. It is. Next, an example of implementation based on the present invention will be shown. In the piping as shown in Fig. 2, the main piping from the shutoff valve 10 is 150A and 18m long, and each of the six branch pipes that branch toward the tuyere is 80A and 8m long.
Furthermore, six tuyeres with a diameter of 18 mm and a length of 1.8 m are installed up to the tip of the tuyere. And the shutoff valve 1 of these pipes
The shutoff valve 10 was installed at a position where the internal volume from 0 to the tip of the tuyere 3 was 0.425 m ³ . Further, as a two-stage diffusion valve, an electromagnetic on-off valve was disposed at a position approximately 6 m from the cutoff valve 10 toward the tuyere 3. In this example, the tilt angle θ of the converter body is 68.9
degree, and the time required to tilt was 8.8 seconds. In this example, no tuyere trouble or deterioration of steel quality occurred due to gas switching. As described above, the converter equipped with the device of the present invention can switch to the required gas without increasing the pressure in the piping before the tuyere is exposed when the furnace is tilted. As a result, the tuyere pine room, bricks, etc. will not be damaged or cracked, and molten steel will not flow back into the tuyere, thereby extending the life of the tuyere.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of a conventional gas switching device, Fig. 2 is a conceptual diagram of a gas switching device according to the present invention, Fig. 3 is a flowchart of the pressure adjustment function in front of the tuyere when the release valve of the present invention is activated, and Fig. 4 is a conceptual diagram of a conventional gas switching device. 5 is a state explanatory diagram of two-stage diffusion according to the present invention, and FIG. 5 is a conceptual diagram in the case of one diffusion valve according to the present invention. 1... Converter, 2... Molten steel, 3... Tuyere, 10, 10'
...Shutoff valve (AV), 11,11'...Control valve (CV),
12, 12'...Check valve, 13...Piping, 14,1
4', 14''...discharge valve, 15,15'...flow meter, 1
6, 16'... Original pressure gauge, 17... Tuyere front pressure gauge, 1
8...Adjusting valve or orifice.

Claims (1)

[Claims] 1. The capacity of the piping from the shutoff valve closest to the tuyere to the tuyere is required to tilt the converter body from an upright position to a tilted position where the tuyere begins to be exposed above the molten steel surface. Bottom blowing gas switching for a converter, characterized in that the cutoff valve is disposed at a position where the capacity is such that gas switching and replacement can be completed in less than the required time t, and a two-stage controlled dissipation device is provided in the piping. Device.