JPS61270321A - Method for blowing gas to liquid - Google Patents

Abstract

PURPOSE:To stabilize jet flow and to make possible the blowing a large amt. of gas at a high speed by blowing the gas of nearly the sonic velocity or the supersonic velocity into the liquid and placing a baffle plate approximately orthogonaly with the top end direction of the jet flow in a bath. CONSTITUTION:The gas 2 is blown into the liquid at the high velocity of >=90% of the sonic velocity thereof and the baffle plate or the solid surface 7 corresponding thereto is placed in the top end direction of the jet flow in the bath orthogonally with the jet flow. Then the gas 2 spouting from a nozzle 1 collides against the baffle plate 7 and forms the foam flow 8 having a spread and heading upward and the circulating flow 9 heading downward. Fine foam 10 is generated over the entire surface in the upper part of the bath and is held up so that the bath surface remains still. The baffle plate or the like 7 is preferably installed in the top end direction 2D-10D from the nozzle outlet when the diameter of the nozzle 1 is designated as D. Bottom beating is thereby prevented and the damage at the nozzle tip is decreased. Blow-by is also prevented and the blowing of a large amt. of the gas at the high velocity is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for blowing gas close to the speed of sound into a liquid.
This is a method of blowing gas that makes it possible to stabilize the jet without the bottom-struck phenomenon, and makes it possible to carry out gas-liquid reactions in the steel industry, chemical industry, etc. extremely advantageously.

BACKGROUND OF THE INVENTION Absorption of a gas into a liquid, reaction of a gas with a liquid (hereinafter simply referred to as gas-liquid reaction), and stirring of a liquid with a gas are 14 processes that are carried out in the steel industry and the chemical industry. For this purpose, it is well known to blow gas into the liquid through a nozzle.

Problems to be Solved by the Invention Regarding the method of blowing gas into a liquid through a nozzle, it is preferable to blow a large amount of gas at as high a speed as possible in order to improve reaction efficiency and shorten operating time.

However, with a straight nozzle where the pipe area of the nozzle is constant, increasing the pressure makes it possible to inject a large amount of gas and maintain a high static pressure at the nozzle outlet, but the speed of sound In order to achieve a flow velocity close to , a large source pressure is required due to the choking phenomenon caused by pipe friction resistance, so it is difficult to flow a large flow rate at low pressure.

On the other hand, if a medium-narrow nozzle or a tapered-wide nozzle (hereinafter referred to as a Laval nozzle) is used, it is possible to easily obtain a jet flow close to sonic speed or supersonic speed, and it is also possible to blow a large amount of gas at low pressure. The jet becomes unstable because the static pressure decreases.

Back attack (bottom hitting phenomenon) is also likely to occur, and damage to the nozzle tip due to back attack becomes significant.

Furthermore, in extremely shallow baths, there is also the concern of blow-through.

The present invention provides a gas blowing method that causes less damage to the nozzle tip and enables high-speed, large-volume gas blowing when blowing gas into a liquid in a jet stream through a nozzle.

Means for Solving the Problems The present invention provides a method for blowing gas into a liquid through a nozzle at a high velocity of 90% or more of the sonic speed, in which a gas is blown into a liquid at a high speed of 90% or more of the sonic speed, and a jet flow is blown in the direction of the tip of the jet flow in the bath, substantially perpendicular to the jet flow. This is a method of blowing gas at near or supersonic speed into a liquid, which is characterized by placing a baffle plate or an equivalent solid surface (hereinafter simply referred to as a baffle plate).

This will be explained below using the drawings (Figs. 1 and 2).

When the gas 2 is blown into the liquid through the nozzle, the process in which bubbles are generated at the tip of the nozzle and then separated is repeated while the flow rate is low.

As the flow rate increases, the frequency of bubble formation and separation increases.
When the flow velocity reaches a high velocity of 90% or more of the sound velocity, the gas phase finally enters the liquid continuously from the nozzle tip. At this time, since the continuous gas phase incorporates liquid, it substantially forms a two-phase flow 3 (there is a core portion 4 containing only the gas phase).

If this region is defined as the bath jet region, the bath jet itself constantly changes its length and shape in the bath, and is essentially unsteady or unstable. The liquid level is showing violent movement up and down.

The biggest factor causing this instability is thought to be interaction with the surrounding liquid. In other words, the jet in the bath grows and invades the liquid due to the inflow of gas from the nozzle, but
As it loses kinetic energy at the tip, it fluctuates under the influence of the movement of the surrounding liquid and causes splitting.
It is often observed in high-speed photographs that the bubble is cut from the constriction 5, but this indicates that even in an area where kinetic energy is still high, the pressure is reduced and the bubble breaks off from the constriction. Conceivable.

Cutting in front of the jet causes a discontinuous and sudden volume reduction of the gas phase or mixture, so if a large amount of gas phase is supplied at a constant speed, a sudden pressure increase and accompanying volume expansion will cause the nozzle to It is thought that this occurs intensively at the outlet, and as a result, the so-called bottom-hitting phenomenon 6 is observed.

In order to reduce the frequency of this bottom tapping, it is effective to increase the gas phase static pressure within the jet (core) to reduce disturbances caused by liquid movement.

On the other hand, the Laval nozzle, which can easily produce high-speed, large-flow gas, has not been put into practical use for blowing gas into liquids.One of the reasons for this is that the pressure at the exit is easily converted into kinetic energy, resulting in supersonic speed. This is thought to be because it is difficult to maintain high static pressure. On the other hand, the generally widely used straight nozzle adopts a blowing speed close to the speed of sound, but this means that this type of nozzle cannot theoretically exceed the speed of sound, so as it approaches the speed of sound, so-called choking occurs. It can be understood that this phenomenon takes advantage of the fact that the gas phase static pressure at the nozzle outlet also rises rapidly, thereby making the jet relatively stable.

However, it is still not possible to avoid disruption due to the unsteadiness caused by the cutting caused by the liquid motion in front of the jet.

Therefore, if a solid wall 7 is provided below the position where this cutting should occur (from the nozzle) and the jet flows along this wall, the steadiness of the jet flow is guaranteed, and the jet flow is continuous and Changes into bubbles at a fixed place,
The entire jet region is stabilized.

The "baffle" 7 of the present invention takes on this role, bearing the hydrostatic pressure on the jet from above, while at the same time providing a flow path and a location for the jet flow to vary continuously.

Therefore, it is possible to form a stable jet even at relatively low pressure and low flow rate, and the bubbles that separate from the periphery of the baffle plate are extremely small compared to normal jet bubbles.

Chemically, this results in an increase in the reaction rate due to an increase in the reaction interface area and residence time, and physically, an increase in stirring power due to an increase in gas hold-up.

This is shown in Fig. 2. The gas 2 ejected from the nozzle 1 collides with the baffle plate 7 located directly above the nozzle, creating an expanding upward bubble flow 8 and a downward ideal circulating flow. 9
form. A fine air @10 is generated all over the upper part of the bath and holds up, and the bath surface 11 is quiet.

Note that the shape of the baffle plate is such that it has a surface (flat surface, curved surface) that substantially covers the spread of the jet flow. The effect does not change if the area is too large, but the effect becomes weaker as the area becomes smaller than the area of the area.

The position a of the baffle plate should be such that it almost covers the spread of the jet stream, the nozzle diameter is D, and the height of the baffle plate surface from the nozzle is H.
Then, 10D≧H≧2D. As aforementioned,
As a guideline, it should be closer to the nozzle side than the cut surface of the continuous gas phase.

The specific method of installing the baffle plate is as follows: (1) Install it from above independently of the nozzle (Figure 3).

(2) The support frame 12 is integrated with the nozzle (FIG. 4).

(3) Insert it inside the nozzle (Figure 5).

There are other methods.

Example 1 Contents @ Fill a 1.25X to' c+a3 water tank with water, and from the nozzle (4 mmφ) at the bottom of the tank, about 3 to 7 kg/c
Air was blown out at a discharge pressure of m2. The flow velocity at this time is close to the speed of sound, and the volume of the jet region is 2.87
X102c+a3. The gas hold up was approximately 0.022 without depending much on the discharge pressure. Also, the back attack was intense.

Next, a baffle plate having a surface that almost covers the spread of the jet stream was installed from above at a location 10+os above the nozzle.
As the air discharge pressure was increased from 3 to 7 kg/cm2, the gas hold up increased from 0.024 to 0.11.

Furthermore, as the baffle plate was brought closer to the nozzle, and as the air discharge pressure was increased, the back attack was observed to decrease (Figure 6).

Example 2 A double tube tuyere (inner tube inner diameter 18 mm, inner tube outer diameter 17 + am, The outer tube has an inner diameter of 20+*m), and the inner tube is filled with oxygen gas or A
Propane gas or N can be supplied to the gap between the r gas and the inner and outer tubes.

In addition, from above, a lance for blowing acid (tip nozzle shape 4m)
mφ, 6 holes) and an iron cylinder whose tip 5.3 mm is coated with refractory (coated portion diameter 200 mm) (the interior is water-cooled above 6 m from the tip). It is designed to be charged inside.

By tilting the furnace, hot metal (C: 4.3%, Si: 0°3%,
1.430℃), and the top blowing lance was charged with oxygen at 12000 N m'/hr, and the bottom blowing lance was charged with oxygen at 3000 N mJ/hr and propane at 50 Nrn'/hr. By blowing, oxidation refining mainly consists of decarburization, and the C content is reduced to 0.3%. Next, the top blowing lance was pulled up to stop the blowing acid, and an iron cylinder whose tip was covered with a refractory was inserted into the furnace, and the tip was lowered to just above the bottom blowing tuyere, under the conditions described above. Then, while keeping the charging conditions of the iron cylinder the same, both gases were switched to Ar (Ar injection amount 200ONrn"/h).
r) Perform blowing for 5 minutes. Finally C: 0.0015
%, 0:0.08%, N: 12ppm, H:
Molten steel with a concentration of 2 ppm and a temperature of 1590° C. is obtained, tapped into a ladle, and after the composition is adjusted, it is poured.

By placing the refractory-coated cylinder (equivalent to a temporary obstruction) directly above the bottom blowing tuyeres, the dispersion of the 02 gas and propane gas blown from one tuyere was promoted.

It was possible to promote decarburization in the low temperature range (and as a result, even with a single tuyere, strong stirring could be maintained and the 0% Fe content of the slag could be reduced) and degassing was promoted.

In addition, during blowing, bubble dispersion is similarly promoted, which increases the contact effect between Ar and molten steel, promotes degassing reactions (by CO reaction and dehydrogenation), and shortens the total blowing time. (7 minutes), reduction in Ar gas consumption rate (approximately 40 minutes)
% reduction).

Example 3 In a container lined with a gutter-like refractory with a width of 1.5 m and a length of 12 m, a double pipe opening (inner pipe inner diameter 10 m1, inner pipe outer diameter Five 12-layer outer tubes with an inner diameter of 14 mm are provided. In addition, from directly above corresponding to the position of each tuyere, we placed an iron cylinder whose tip part was 1.3 m covered with refractory material (the diameter of the covered part was 200 m2, the diameter of the iron cylinder was 100 m1, the refractory The portion above 1.5 m from the tip of the coated portion is water-cooled).

From one end of this furnace, C::1.5% molten steel is poured at 3 t/wi.
At the same time, oxygen (from the inner tube) and propane (from the gap between the inner tube and the outer tube) are supplied at a rate of 100 nia from each bottom blowing tuyere.

An iron cylinder with a refractory-coated tip was placed directly above each tuyere as a baffle plate.

With this method, even though the molten steel depth is small, bottom-blowing refining can be performed stably and low-grade molten steel with C: 0.1% or less can be produced while keeping the degree of peroxidation of the slag small. did it.

Effects of the Invention As detailed above, in the present invention, by placing a baffle plate or an equivalent solid surface at the tip of the jet in the bath, the jet stream collides with this surface and flows along this surface. , which means that a (fixed) flow field is ensured for the jet flow6, thereby stabilizing the jet.

By stabilizing the jet, the following remarkable effects can be obtained.

(1) The bottom-slapping phenomenon becomes rare, and damage to the nozzle tip is greatly reduced.

(2) Since there is no concern about blow-through, it is possible to blow a large amount of gas at high speed even in an extremely shallow bath.

(3) It is possible to stably blow a large amount of gas even at a lower pressure than is normally employed in a no-straight nozzle.

(4) Bubbles become fine particles.

the result, ■The gas-liquid interfacial area increases, which is extremely advantageous for gas-liquid reactions.

■The hold-up amount increases and the residence time of bubbles in the liquid increases, which is advantageous for gas-liquid reactions.

■Increases the stirring effect, especially in shallow baths.

Therefore, 1. The present invention provides a steelmaking furnace, a bottom blowing tuyere in a steelmaking furnace, a blast furnace casting bed treatment, and 1! ! Applicable to gas injection into relatively shallow molten metal flows such as continuous steelmaking furnaces and trough-type continuous steelmaking furnaces, deoxidation, denitrification, and dehydrogenation by large amounts of gas injection in ladle refining, inclusion separation in tundish, etc. sexual,
The industrial value is great.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams for explaining the present invention in detail. 3 to 5 are elevational views illustrating a specific method of installing baffle plates. Figure 6 is a diagram showing the relationship between nozzle diameter, level, gas discharge pressure, and back attack frequency.
・e11 core, 5◆war・〈fin, 6...bottom slap, 7
...baffle plate, 8...bubble flow, 9.so circulation flow, 1
0...Fine bubbles, 11φ...Bath surface, 12...Support frame.

Claims (3)

[Claims] (1) In a method in which gas is blown into a liquid through a nozzle at a high velocity of 90% or more of the sonic speed, a baffle plate or a solid surface equivalent to the baffle plate or a solid surface corresponding to the jet stream is placed approximately perpendicularly to the jet stream in the direction of the tip of the jet stream in the bath. (hereinafter simply referred to as a baffle plate) A method of blowing gas at near or supersonic speed into a liquid. (2) When the diameter of the blowing nozzle is D, the baffle plate or an equivalent solid surface is installed in the distal direction at least 2D and approximately 10D or less from the nozzle outlet.
1) Method of blowing gas into the liquid described in section 1). (3) A method for blowing gas into a liquid according to claim (1), wherein the liquid is a molten metal.