JPS6140013B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a converter having a bottom blowing function. A converter with a bottom-blowing function has a bottom tuyere through which N ₂ , which is virtually inert to oxidizing gases and/or molten metal, is pumped.
Refining vessels, such as so-called top-bottom-blown converters, in which oxidizing gas and Ar are blown in together with oxidizing gas by a top-blowing lance, as in an LD converter, and bottom-blown converters, in which the above-mentioned gas is blown only from the bottom tuyere. shall refer to. During blowing in a converter of the type mentioned above, the contents in the furnace are vigorously stirred, so during steelmaking and refining, the iron concentration (T Fe) in the slag is lower than that in an LD converter. In addition to the advantage of significantly lower iron yield and improved iron yield, the decarburization rate is particularly high in the low coal range, and it also has excellent desulfurization ability. Because the charging bath is accompanied by strong vibrations at a constant period due to the stirring action of
Vibration prevention measures are required when installing the converter main body. Therefore, in the case of converters installed exclusively for bottom blowing, various measures were taken to support the converter, whereas conventional LD converters usually do not produce the above-mentioned vibrations. When adding a bottom blowing function to this converter and attempting to perform a combined top and bottom blowing operation, it lacks the vibration prevention measures of a bottom blowing converter, and the cost of modifying the support structure increases enormously. This hindered the use of the LD converter as a top-bottom blowing converter, and if conversion were to be carried out without modification, the support frame would not be able to withstand the intense vibrations, leading to damage to the furnace body. , durability may inevitably deteriorate, leading to a serious accident. This invention facilitates conversion to top and bottom blowing combined blowing in an LD converter by particularly advantageously preventing the blowing vibrations that are characteristic of converters with a bottom blowing function as described above. In addition, we will propose the results of the development of an operating method that can eliminate the need for solid installation when installing a bottom-blowing converter. The severe vibrations in a converter with a bottom-blowing function are forced vibrations whose main external force is the vibration caused by the strong stirring that occurs in the charging bath, so reducing the bathing vibration inside the furnace is the key to reducing converter vibration. It is an object of the first invention to reduce the vibration of the charging bath without reducing the stirring action. Next, when trying to add a bottom-blowing function to the LD converter mentioned above, the profile of the furnace body is such that the bottom-blowing converter has a wide belly compared to its height, as shown in Figure 1. On the other hand, as shown in Figure 2, the furnace belly generally has a narrow body length, so the bottom blowing tuyeres are immersed in the tilted position for charging hot metal, and the furnace body is immersed until the bottom blowing gas is supplied. In order to avoid loss of chromium, especially in stainless steel blowing operations, it is considered advantageous to increase the depth of the bath. The second problem is to advantageously avoid this problem by suppressing the converter vibration.
This is the object of the invention. In this invention, a plurality of bottom blowing tuyeres opened in a row at intervals from each other in the furnace bottom are spaced at a distance corresponding to 0.025 to 0.1 times the furnace bottom diameter parallel to the trunnion axis of the furnace body. The solution to the above basic problem is to use eccentric arrangement with an arrangement area width that is within 0.75 times the diameter of the furnace bottom. The solution to the second problem is to
It is desirable that the diameter be at least 0.2 times the furnace bottom diameter, and that the tuyeres be arranged in a straight line. The above-mentioned eccentric arrangement is derived from experimental findings that it is particularly effective in damping converter vibrations, as will be described in detail below regarding its development progress and its application to actual furnace operation. Eccentricity is caused by the fact that when charging the converter, the furnace body is tilted with the tapping side, that is, the side with the tapping hole, facing up. Therefore, immersion due to this can be effectively avoided. In researching the development of this invention, the inventors first compared water to molten metal and conducted a so-called converter water model experiment to determine the arrangement of the bottom blowing tuyere and the shape of the furnace. We obtained the knowledge that the vibration behavior of the baths is different, and confirmed this using the hot model and the measurement results of the actual furnace. Now, in the water model, which is equivalent to 1/20 scale down of the 80-ton bottom blowing converter, the vibration behavior of the bath that occurs in the transparent acrylic resin model water tank is simulated by simultaneous top blowing of 153/min and bottom blowing of 51/min. In this case, on the bottom wall of the aquarium with an inner diameter D of 365 mm as shown in Figure 3,
Several fumarole pipes with various distances to their diameters are arranged over various array area widths L,
We measured the acceleration of vibrations occurring in the model aquarium and obtained the results shown in the table below.

【table】

[Table] Based on the results of this basic experiment, L/D is
0.75 or less, the acceleration is minimum in each case where /D is 0.025 to 0.10.
Test blowing was conducted using a top and bottom blowing experimental converter under the following conditions. The furnace bottom wall 1 with a furnace bottom diameter D100 mm is made removable according to the customary practice in bottom-blowing converters, and the bottom-blowing tuyere 2 is replaced with a cassette type so that the values of L and are different. Port 2 has an inner diameter of 8
Bottom-blown oxygen amount is 5.0N using mmφ double tube tuyeres.
m ³ /min, and the top blowing oxygen amount was set at 7.5 Nm ³ /min using the top blowing lance 3, and the vibration acceleration was measured in a direction parallel to the furnace trunnion axis for 7 to 8 minutes after the start of blowing. At the same time, the amount of brick wear on the tapping side and trunnion side after each blowing was also measured. In FIG. 2, 4 indicates hot metal, 5 indicates slag, and 6 indicates the blowing point. Note that the corresponding numbers are commonly used in the case of the bottom blowing converter shown in Fig. 1. Figure 4 also shows the tilting posture for charging hot metal.
is the tap hole. The results of each test blowing are /D in the case of L/D0.575.
Figure 5 summarizes the influence of the
Figure 6 summarizes the trends that L/D has on acceleration and trunnion side brick wear over the range of . First, looking at the transition of acceleration as /D changes in Figure 5, when /D=0, that is, when the bottom blowing tuyeres 2 are arranged along the diameter of the hearth bottom, the acceleration is approximately
0.04G, but when eccentricity is set to /D=0.025, until it reaches 0.1, it is halved to about 0.02G and remains almost constant, but when /D exceeds 0.1, it reaches 0.15 and becomes 0.05G. It will rapidly increase until it reaches On the other hand, the amount of loss of bricks on the tapping side increases rapidly when /D exceeds 0.1 and reaches 0.15, but when /D≦0.1, it is so slight that it does not reach 1.5 mm/heat. Next, according to FIG. 6, it was confirmed that the influence of L/D acceleration and trunnion side brick wear significantly increases when L/D exceeds 0.75 compared to when L/D exceeds 0.75. According to the above confirmation experiment, the damping results of the water model experiment described above are reflected almost directly in the actual reactor operation.
According to this invention, it has been experimentally verified that an effective reduction in furnace vibration can be reliably brought about even when a bottom blowing function is added to an originally long-boiled LD converter. It should be noted that almost the same results can be obtained not only when the bottom blowing tuyeres are arranged in a straight line as shown in FIG. Therefore, according to the first invention, when used in a bottom blowing converter, it is possible to simplify the support structure and foundation to withstand severe vibration therein, and also to add a bottom blowing function to the LD converter. In that the reinforcement of the support frame conventionally required for top-bottom blowing is virtually unnecessary, a remarkable effect on vibration suppression of the converter is brought about as well as a marked reduction in wear and tear on the furnace body. Further, according to the second invention, the bottom blowing tuyere is advantageously separated from the charging bath surface under the charging tilting posture of the furnace body, and wear due to immersion can be advantageously avoided, so that it is also possible to blow stainless steel. The effects that can be well matched are
More will be added.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a bottom blowing converter, Figure 2 is a LD
Cross-sectional view of a top-bottom blowing converter utilizing a converter body, Part 3
Figure 4 is a plan view of the bottom of the furnace, Figure 4 is a sectional view showing the tilted charging posture, and Figures 5 and 6 are respectively
It is a graph showing the influence of /D and L/D on the acceleration of furnace body vibration and furnace wall wear. 1... Hearth bottom, 2... Tuyere, 3... Lance,...
...distance, L... array area width, D... hearth bottom diameter.

Claims (1)

[Scope of Claims] 1. A plurality of bottom blowing tuyere openings in a row at intervals from each other at the furnace bottom are provided with a diameter corresponding to 0.025 to 0.10 times the furnace bottom diameter parallel to the trunnion axis of the furnace body. A bottom-blowing converter is characterized in that it is eccentrically arranged with a distance between the two and an arrangement area width that is within 0.75 times the furnace bottom diameter. 2 The width of the array area of multiple bottom blowing tuyeres is equal to the furnace bottom diameter.
The converter according to claim 1, which is 0.2 times or more. 3. The converter according to claim 1 or 2, wherein the plurality of bottom blowing tuyeres are arranged in a straight line. 4 A plurality of bottom blowing tuyeres opened in a row at intervals from each other at the furnace bottom are biased toward the tapping side of the furnace body with respect to the furnace bottom diameter parallel to the trunnion axis of the furnace body, and the furnace bottom diameter is 1. A bottom-blowing converter characterized in that the bottom blowing converter is eccentrically arranged with a distance equivalent to 0.025 to 0.10 times the diameter of the hearth and an array area width within 0.75 times the hearth bottom diameter. 5 The width of the arrangement area of multiple bottom blowing tuyeres is equal to the furnace bottom diameter.
The converter according to claim 4, which is 0.2 times or more. 6. The converter according to claim 4 or 5, wherein the plurality of bottom blowing tuyeres are arranged in a straight line.