JP3029505B2 - How to blow gas into molten metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for blowing gas into molten metal in metal refining.

[0002]

2. Description of the Related Art There are many industrial fields in which a gas is blown into a liquid to stir the liquid to make the temperature and concentration in the liquid uniform and to promote the reaction. In metal refining, for example, promotion of contact between molten iron and slag in a smelting reduction furnace, stirring of molten steel in a converter, dispersion of bubbles in a riser in RH degassing, dephosphorization in a ladle refining,
It is used over a wide range such as stirring a desulfurizing agent. The gas temperature in this case is significantly lower than the melt temperature.

[0003]

However, in a smelting vessel in which a tuyere is provided on the side wall of the vessel and gas is blown horizontally or obliquely to promote the reaction of the molten metal and to make the temperature and concentration uniform, the blown gas is in the molten metal. Is difficult to be dispersed in the horizontal direction, and
Due to rapid expansion due to heat transfer from the molten metal, the bubbles rise near the side wall, causing wear of the refractory inside the container.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a high-temperature gas having a temperature equal to or higher than the temperature of a molten metal is blown into the molten metal at a high speed from a side wall of the container toward the center of the container.
Disperse air bubbles in the molten metal, improve the stirring efficiency of the molten metal,
It is another object of the present invention to provide a method for blowing gas into a molten metal, which reduces wear of a refractory inside a container.

[0005]

The gist of the present invention is that a nozzle is provided on the side wall of a container, and a high-temperature gas at a temperature higher than the temperature of the molten metal is supplied from the nozzle toward the center of the container at a speed of at least Mach 1.0 in the container. This is a method of blowing gas into the molten metal.

[0006]

The present inventors have investigated the behavior of gas bubbles blown into the molten metal. In this type of technology, there is no means for observing the behavior of air bubbles, measuring the flow velocity, etc. The fact is that it is necessary to evaluate the experiment used.

Therefore, the inventor has added room temperature air to room temperature water,
The behavior of bubbles was investigated by blowing low-temperature nitrogen gas. The experimental device is shown in FIG. The compressed gas from the compressor or cylinder 1 is supplied to the regulator 2, the mass flow meter 3
To the cooler 4, where it is cooled by liquid nitrogen 8 at normal pressure. The cooler 4 is provided with a bypass that bypasses the cooler 4. The gas that has passed through the cooler 4 or the bypass is blown into normal-temperature water from a nozzle 6 provided on the side of the container 5. Normal temperature air passed through the bypass, and low temperature nitrogen gas passed through the cooler 4. Container 5 has an inner diameter of 300 mm and a height of 3
50 mm, the distance from the nozzle to the water surface is 200 mm, and the inner diameter of the nozzle 6 is 1 mm.

[0008] The gas hold-up (the average value of the volume ratio of bubbles in the liquid) was measured by an electric probe method. The gas hold-up was obtained from the data obtained by AD-converting the output signal of one electric probe 7 at a sampling frequency of 5 kHz. Table 1 shows the experimental conditions.

[0009]

[Table 1]

FIG. 1 shows the radial distance (Rr) from the side wall of the container.
Fig. 2 shows the gas hold-up in the vertical section of each container, and Fig. 2 shows the gas hold-up in the radial direction (transverse section) from the container side wall, and plots the maximum value for each cross-section, showing the trajectory of bubble rise. It is.

In FIG. 1, the circle indicates that the gas temperature is the same as the water temperature (normal temperature), so that the bubbles are dispersed far from the tip of the nozzle. At this time, the Mach number of the gas at the nozzle outlet is 1.11.
It is. On the other hand, the open squares indicate that the gas temperature is room temperature, but the mass flow rate of the gas is small, so that the dispersion of bubbles is poor, and the Mach number at the nozzle exit of the gas at this time is 0.59. The △ mark shows the same gas mass flow rate as the ○ mark, but because of the low temperature,
The dispersion of bubbles is poor, and the Mach number at the gas nozzle outlet at this time is 0.85. That is, the mark “△” behaves in the same manner as the normal-temperature gas blowing with the same volume flow rate (marked with “□”).

FIG. 2 shows the trajectory of the bubble rise as described above. It can be seen that the gas with a high temperature (marked by ○) has bubbles dispersed far from the tip of the nozzle and rises. In addition, the low-temperature gas (marked with “△”) has a small dispersion of bubbles, and the bubbles return to the side wall of the container during the rise.

[0013] Thus, the constraints of the present invention from the above findings, the temperature of the gas blown from the nozzle provided in the side wall of the container to the container center direction in the melt is a high temperature, the above melt temperature. Also, the blowing speed should be at least Mach 1.0.

By blowing gas into the molten metal under the above-described restrictions, bubbles can be dispersed in the molten metal, the efficiency of stirring the molten metal can be improved, and the wear of the refractory inside the container can be reduced.

[0015]

Embodiments of the present invention will be described below. In a ladle refining furnace with a horizontal tuyere, 16
Ar gas heated to a high temperature of 00 ° C. was blown into the molten steel at Mach 1.2 to stir the molten steel. As a result, the bubbles of the Ar gas were dispersed in front of the tuyere, and did not rise near the furnace wall, thereby reducing the wear of the refractory lining. In addition, since the bubbles are dispersed and rise, the stirring efficiency is improved, and the molten steel temperature and the molten steel component can be made uniform in a short time. In addition, for the heating of the blown gas, a tuyere having good heat conductivity can be used, and heat from the molten metal can be used.

[0016]

According to the present invention, a nozzle is provided on a side wall of a container,
The hot gas above the molten metal temperature from the nozzle a gas blowing method of the melt blown into molten metal in the container vessel center direction Mach 1.0 or faster, according to the present invention method, by dispersing the gas bubbles into the melt In addition, the stirring efficiency of the molten metal can be improved, and the wear of the refractory inside the container can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing gas hold-up for each radial distance from a container side wall.

FIG. 2 is a diagram showing a trajectory of bubble rise.

FIG. 3 is a view showing an experimental apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor or cylinder, 2 ... Regulator, 3 ... Mass flowmeter, 4 ... Cooler, 5 ... Container, 6 ... Nozzle, 7 ... Electric probe probe, 8 ... Liquid nitrogen.

Claims (1)

(57) [Claims] 1. A nozzle is provided on a side wall of a container, and a hot gas having a temperature equal to or higher than the temperature of a molten metal is supplied from the nozzle toward a center of the container.
A method for injecting gas into a molten metal, wherein the gas is injected into the molten metal at a speed of 1.0 or more.