JPS6210284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a top-bottom blowing converter or a bottom-blowing converter having a bottom-blowing function in which the bottom-blowing tuyeres of the converter are rationally arranged. In a converter with a bottom-blowing function, the contents inside the furnace are vigorously stirred during blowing, so during steelmaking and refining, the iron concentration (T.Fe) in the slag is significantly lower than in an LD converter. It has the advantage of improving iron yield, and in addition, has a high decarburization rate especially in the low coal range, and also has excellent desulfurization ability. However, the gas blown in from the bottom blowing tuyeres violently agitates the steel bath as described above, causing large vibrations in the steel bath at a constant period. Therefore, in a bottom-blowing converter as shown in Figure 1, various anti-vibration measures are taken in the support mechanism of the converter in order to prevent the entire converter from undergoing large synchronous vibrations due to vibrations in the steel bath. . On the other hand, in conventional pure oxygen top-blown converters, there is almost no periodic vibration of the entire steel bath. Not as much consideration has been given to the design as in the case of blow-only converters.
Therefore, if an existing top-blowing converter is converted into a bottom-blowing converter and used as a pure oxygen bottom-blowing converter,
The converter itself vibrates greatly, making operation unstable, and the support mechanism may not be able to withstand the large vibrations of the converter and may be damaged or deteriorate early, leading to a serious accident. In order to prevent this, it would be possible to modify the support mechanism of the converter, but such modification would be extremely large-scale and the cost would increase significantly.
The cost is not much different from manufacturing a bottom-blown converter from scratch, and the economic benefits of modifying an existing top-blowing converter are lost. For these reasons, conventionally, existing top-blown converters have rarely been modified to become bottom-blown converters, and although the advantages of bottom-blowing converters are recognized, conversion to bottom-blowing converters has been difficult. The reality is that progress has been slow. Furthermore, in bottom-blown converters, there were problems such as molten iron being blown flowing out of the tapping port and damage to the sub-lance probe due to large periodic vibrations in the steel bath caused by bottom-blowing gas. . On the other hand, as shown in Figure 2, in order to incorporate the advantages of a bottom-blowing converter into an existing top-blowing converter, a top-bottomed converter that uses a combination of blowing from the top-blowing lance and blowing from the bottom-blowing tuyere. Blown converter steelmaking is also being tried. In this case, the flow rate of the blown gas from the bottom-blowing tuyeres is considerably smaller than in the case of a pure bottom-blowing converter, so the vibration of the steel bath is also small. However, compared to a top-blown converter, the periodic vibration of the steel bath is considerably large, and the converter also vibrates considerably, so there are problems similar to those described above, albeit to a different degree. A converter with a bottom-blowing function also has the disadvantage that the bottom bricks are worn out due to periodic vibrations, resulting in an increase in the unit cost of refractories. The present invention suppresses the vibration of a converter with a bottom-blowing function, that is, the steel bath vibration, by optimizing the arrangement of bottom-blowing tuyeres, reduces the cost of refractories, and reduces the cost of existing top-blowing converters. The object of the present invention is to provide a measure for easily modifying a bottom-blowing converter or a top-bottom blowing converter to provide a bottom-blowing function. The present inventors reduced the steel bath vibration without reducing the in-furnace stirring effect of a converter with a bottom-blowing function.
We conducted development research to reduce furnace body vibration. The present invention uses a so-called converter water model to confirm through experiments the causal relationship that the arrangement of bottom blowing tuyere greatly affects the vibration intensity of the bath. It is something that The water model experiment will be explained next. The vibration behavior of the bath generated in a transparent acrylic model water tank was measured in a reduced water model equivalent to 1/10 of an 80-ton bottom-blown converter. The furnace bottom diameter D shown in Figure 3 is
Several fumarole pipes are arranged on the bottom wall of the 365 mm water tank on a line parallel to the constant diameter line of the bottom of the furnace, and the top blowing 153/
Simultaneous blowing was carried out at a rate of 51/min and bottom blowing at 51/min. The fumarole pipes on the bottom wall of the aquarium are arranged on two lines that are parallel to a certain diameter line of the bottom wall and whose horizontal distance from the diameter line is l ₂ , with the maximum arrangement areas L ₁ , L ₂ , non- It was placed in the array area _l1 , and the vibration intensity generated in the model tank was measured. Tests were conducted with various changes in L ₁ , L ₂ , l ₁ , and l ₂ . Furthermore, using the same tuyere arrangement, the uniform mixing time in the bath, which is a measure of the stirring intensity in the furnace, was also measured, and the results shown in Table 1 were obtained. As a result of this basic experiment, the vibration intensity is small when L ₁ /D is 0.38 to 0.80, l ₁ /D is 0.19 to 0.58, L ₂ /D is 0.28 to 0.69, and l ₂ /D is 0.025 to 0.30. It was discovered that the stirring capacity was not reduced. From Table 1, it is clear that the steel bath vibration intensity decreases as the tuyere arrangement position moves away from the core. On the other hand, the uniform mixing time, which is a guideline for the stirring strength of the bath, is 20 seconds when L ₂ /D is 0.73 or more.
This is the above, and the stirring ability is not good. If L ₂ /D is 0.69 or less, the value of l ₂ /D is 0.01
Even when the value of l ₂ /D is 0.35, the stirring performance is not good. The above L ₂ /D is 0.69 or less, and l ₂ /D is 0.025
-0.30 shows excellent stirring ability. This is presumed to be due to the interference effect between the gas jet from the top blowing lance and the gas jet from the bottom blowing tuyere, which promoted the stirring ability. Next, an example of a 5t top-bottom blowing experimental converter will be shown. The furnace bottom wall 1 with a furnace bottom diameter of 1000 mm as shown in Fig. 2 is made removable, and the bottom blowing tuyere 2 is installed as a cassette type so that the values of L ₁ , _{L 2} and l ₁ , l 2 are different. I made a change. This bottom blowing tuyere 2 has an inner diameter of 8
The amount of bottom-blown oxygen using mmφ double tube tuyere is
Test blowing was conducted with the oxygen flow rate set at 5.0Nm ³ /min and the amount of top-blown oxygen by the top-blowing lance 3 set at 7.5Nm ³ /min. After the start of blowing, the uniform mixing time of the steel bath was determined by the method shown in FIG. Since the uniform mixing time of the steel bath is 1 to 2 minutes at most, it is difficult to examine changes in the concentration of the steel bath by continuous sampling. Therefore, the uniform mixing time was determined by sampling at different locations at the same time, adding the tracer, and determining whether or not it was uniform based on the sampling time. A Cu wire with a thickness of 1 mm was used as a tracer, and sample collection was performed using a sampler 7 having a width w of 450 mm and consisting of three bombs 8 as shown in FIG. 6th
The figure shows an example of the measurement. In Figure 6, the horizontal axis shows the time after tracer addition, and the vertical axis shows the time in the steel before adding Cu.
Cu concentration is Cuo, Cu concentration in steel at time t is
Cut, Cu concentration in steel after complete mixing is Cuf, (Cut
-Cuo)/(Cuf-Cuo). At the same time, the amount of brick loss at the bottom of the furnace after each blowing process was also measured. The results of each test blowing are as follows: L ₁ /D is 0.38 to 0.80 L ₁ /D is 0.19 _to 0.58 L ₂ /D is 0.28 to 0.69 Figure 7 shows the effects. Also, for l ₂ /D in the range of 0.025 to 0.30,
FIG. 8 shows the tendency that L ₁ /D has on the uniform mixing time and the amount of wear of the furnace bottom bricks. First, looking at the change in uniform mixing time as l ₂ /D fluctuates in Figure 7, when l ₂ /D = 0, that is, when the bottom blowing tuyeres 2 are arranged along the diameter of the hearth bottom, Uniform mixing time is approx.
It is 40 seconds. When l ₂ /D is eccentric to 0.025 to 0.30, the uniform mixing time shows a value of about 22 to 26 seconds. When l ₂ /D exceeds 0.30 and reaches 0.35, the uniform mixing time increases to about 40 to 42 seconds. On the other hand, the amount of wear on the furnace bottom bricks shows a large value of approximately 5 mm/heat when (a) l ₂ /D=0. (b) When l ₂ /D exceeds 0.025 and reaches 0.30, it is approximately 2 to 3
It rapidly decreases to mm/heat. (c) Even when l ₂ /D exceeded 0.30 and was within 0.35, it remained almost constant. Next, according to Fig. 8, the influence of L ₁ /D on the uniform mixing time and the amount of wear of the furnace bottom bricks is as follows:
It was confirmed that when L ₁ /D is in the range of 0.38 to 0.80, the uniform mixing time is short and the amount of wear of the furnace bottom bricks is also small. As a result of the above confirmation experiment, the damping buildup of the water model experiment described above is reflected almost directly in the actual reactor operation.
It has been experimentally demonstrated that the present invention can reliably reduce furnace body vibration even when a bottom blowing function is added to an LD converter that originally has a long body as shown in Figure 2. It was. Therefore, by employing the bottom-blowing tuyere arrangement of the present invention, it has become possible to simplify the support structure and foundation for withstanding severe vibrations in the bottom-blowing converter. Furthermore, according to the present invention, in the case of adding a bottom blowing function to an LD converter as shown in Fig. 2,
Reinforcement of the support frame, which was conventionally required for top-bottom blowing, is virtually unnecessary. As described above, the present invention is extremely effective in suppressing converter vibrations, and also brings about the effect of significantly reducing wear and tear on the furnace body and furnace bottom bricks. 【table】

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a bottom blowing converter, Figure 2 is a LD
A vertical cross-sectional view of a top-bottom blowing converter utilizing a converter body, Figure 3 is a plan view of the furnace bottom, Figure 4 is a schematic cross-sectional view of a converter showing a method for measuring uniform mixing time, and Figure 5 is a sampler. Fig. 6 is a graph showing an example of measurement of uniform mixing time, Fig. 7 is a graph showing the effect of l ₂ /D on uniform mixing time and the amount of wear of furnace bottom bricks, and Fig. ₈ is a graph showing an example of measurement of uniform mixing time. It is a graph showing the influence of D on the uniform mixing time and the amount of wear of furnace bottom bricks. 1... Hearth bottom, 2... Bottom blowing tuyere, 3... Lance, 4... Steel bath, 5... Slag, 6... Flash point, 7
... Sampler, 8... Bomb.

Claims (1)

[Claims] 1. A top-bottom blowing converter or a bottom-blowing converter, characterized in that the bottom blowing tuyere is arranged on a line parallel to the diameter line of the hearth bottom so as to satisfy the following conditions: A converter with a bottom blowing function. (1) 0.38≦L ₁ /D≦0.80 (2) 0.19≦l ₁ /D≦0.58 (3) 0.28≦L ₂ /D≦0.69 (4) 0.025≦l ₂ /D≦0.30 where, D: Furnace Diameter of the hearth bottom parallel to the trunnion axis of the body L ₂ : Horizontal distance between the hearth bottom diameter line parallel to the trunnion axis and the tuyere installation line L ₁ : Parallel to the hearth bottom diameter line and toward the tapping side l ₂
The maximum area width of the tuyere on the tuyere installation line with a fairly eccentric arrangement l ₁ : Parallel to the diameter line of the furnace bottom and toward the tapping side l ₂
Non-disposed width of the tuyere within the maximum area width of the tuyere on the tuyere arrangement line _L2 : A tuyere that is parallel to the diameter line of the hearth bottom and eccentrically arranged to the charging side by _L2 Maximum area width of tuyere on installation line