JPH01208411A - Method for cooling gas nozzle in smelting metal furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for cooling a gas nozzle disposed below the bath surface of a molten metal furnace, and is used, for example, in the refining of molten steel or the production of flammable gas using an iron bath. The present invention can be widely applied to processes in which oxygen or an oxygen-containing gas is blown into a molten metal bath through a gas nozzle to cause an exothermic chemical reaction in processes and other processes.

(Conventional technology) The conventional technology will be explained below using molten steel refining as an example.

In recent steelmaking technology, the direction has shifted from the LD converter method in which oxygen is blown in from an upper lance to the oxygen bottom blowing method using a nozzle installed below the bath surface (or a compromise method in which oxygen is blown in from above and below). Things are changing. At this time, the temperature at the tip of the nozzle installed below the bath surface (hereinafter referred to as the bottom blowing nozzle) reaches a significantly high temperature due to the reaction between the bath and oxygen.
At the same time, it shortens the life of the nozzle itself and the surrounding bricks.
It is well known that techniques for protecting the nozzle have been invented and used in response to the problem of production of a large amount of metal fume and reduced yield.

For example, in Tetsu to Hagane, 65 (1979), p. 138,
It describes the cooling of the nozzle.

By the way, when hydrocarbons are used in this way, the nozzle tip is cooled by the increase in sensible heat and decomposition heat of the hydrocarbons, and a solidified substance called pine mushroom adheres around the nozzle and acts as a protector.

Moreover, it was discovered that top-blowing of oxygen alone, as in the LD converter, does not provide sufficient agitation of the bath, and that a certain amount of bottom-blowing produces good results in terms of yield and other aspects. It became essential. Against this background, cooling technology for gas blowing nozzles placed below the bath surface is becoming increasingly important.

(Problems to be Solved by the Invention) As explained in the previous section, C3H1l and other hydrocarbons work extremely effectively as bottom-blowing nozzle coolants, but there are several problems in actual use. It is inevitable that there will be points. For example, C3H,I requires 2 to 3% of the amount of oxygen blown from the same nozzle, resulting in a considerable increase in cost.

In addition, in c and n8, different concentric tubes are usually inserted outside the oxygen nozzle to flow through an annular gap with the internal oxygen tube, so the diameter of the entire nozzle must be increased accordingly. In particular, when blowing carbonaceous material at the same time as oxygen, a triple tube nozzle is used, which becomes increasingly large in diameter. In bottom-blowing nozzles, there is always a risk of molten metal entering the nozzle, and it is generally considered that this risk is greater as the nozzle diameter increases, so increasing the diameter by the CJs flow path is not a desirable direction.

Another problem is iron fume generated from within the bath directly above the nozzle. Although there are various theories as to the cause of iron fume generation, it is predicted that the temperature directly above the nozzle that blows oxygen reaches a considerable temperature, and it is safe to assume that this temperature is the main cause of iron fume generation. .

Regarding iron loss due to dust generated in iron bath furnaces, there are other causes besides fume, such as so-called bubble bursts when air bubbles burst on the bath surface, but the loss due to fume also accounts for a considerable proportion. It is clear from the fact that fine spherical particles of several hundred angstroms or less are observed under an electron microscope.In order to reduce this fume "f!", it is necessary to lower the temperature of the high temperature part as much as possible. It is.

Increasing C3H81 has the effect of causing pine mushrooms to enlarge, so it is effective in lowering the temperature, but
It is inevitable that there will be problems in terms of cost.

The present invention was made to solve the above problems, and provides a method for cooling a gas nozzle that protects the nozzle and improves yield.

(Means for Solving the Problems) The present invention is characterized in that atomized water is used instead of conventional hydrocarbons and directly added to an oxygen-containing air stream, and has the following gist.

That is, in a method in which oxygen or an oxygen-containing gas is supplied into molten metal through a gas nozzle placed below the bath surface of a molten metal furnace to cause a chemical reaction that generates heat, oxygen is or a cooling method for a gas nozzle of a molten metal furnace, characterized in that the gas is suspended in an oxygen-containing gas and supplied to the gas nozzle; Either a high flow rate section is provided and water is injected from a nozzle into this high flow rate section, or a water injection nozzle is provided that penetrates the pipe wall in the oxygen or oxygen-containing gas flow path behind the nozzle, and the pressure immediately before the water nozzle and the oxygen Alternatively, water is injected from the nozzle with a gas pressure differential of oxygen-containing gas of 0.3 kg/aa or more, or water is injected from a water injection nozzle provided in a high flow rate part of the bottom blowing nozzle body, Water is atomized by using any one method or a combination of two or more of the methods that utilize the dynamic pressure of high-velocity airflow.

(for production) Hereinafter, the present invention will be explained in detail along with its operation.

The nozzle cooling effect of hydrocarbons is interpreted to be due to the increase in sensible heat and heat of decomposition after being blown into the bath.

Therefore, in place of these hydrocarbons, the present inventor proposed gases that are inexpensive and can be expected to remove a large amount of heat in the bath.
We focused on water or water vapor as a liquid. In particular, the enthalpy of evaporation of water is large because the molecules of water are associated by hydrogen bonds, and evaporation takes place at low temperatures.This prevents excessive rise in the bath temperature at the tip of the nozzle, protects the nozzle, and generates metal fume. It was expected that the amount would decrease.

Furthermore, unlike hydrocarbons, there is no danger in flowing water into the oxygen flow path of the nozzle, so it is possible to reduce the diameter of the entire nozzle without requiring a special flow path.

Table 1 shows a comparison of cooling capacity.
Taking Js, steam, and water as examples, the required amount was calculated assuming that the sensible heat increase of the coolant up to 1100°C and the heat removed by evaporation are useful for nozzle protection.

In addition, when water or steam is blown into the bath,
Heat removal by the water gas reaction H2O+ (C) → co + lh is also quite conceivable, but since this reaction occurs in the bath, it is assumed that it does not take part in cooling the area directly above the nozzle, and the cooling effect due to the reaction is considered to be I don't expect that. (
Table 1 shows an example of calculation for water vapor. ) According to this calculation result, by adding 66 g of liquid water to 1 kg of oxygen, the conventional INI'rr per oxygen can be reduced by 0.
This means that the same cooling effect as when using 03 Nn-r C3H5 can be expected.

This value is half that of water vapor (sensible heat only), which is significantly smaller in terms of weight, and compared to steam which requires special equipment such as heat insulation, water requires extremely simple thin piping. You can reach your goal.

From the above calculations, water is an extremely excellent nozzle coolant that can replace hydrocarbons.

Table 1 (Example) Examples of the present invention will be described below.

Figure 1 shows a vertical cross section of a test iron bath furnace with a molten iron capacity of 40 kg, in which a gas nozzle 1 is inserted from the upper part of the furnace into the iron bath 9 of a crucible 8, and the crucible 80 can be electrically heated 12 from the circumferential surface. . Note that the top of the crucible 8 is covered with a lid 10.

Pig iron was inserted into a crucible 8 in advance, and electrically heated 12 from the surrounding area to melt it. The temperature of the molten iron 9 was detected by inserting a small sub-lance probe into the upper measurement hole, and the experiment was conducted in the range of approximately 1250"C to 1350°C. The C% in the molten iron was in the range of 2 to 4%. After the temperature rose to a predetermined temperature, nozzle 1 lined with castable or plastic refractories (channel inner diameter approximately 10
m/m, outer diameter 50 to 60 m/m) was inserted into the iron bath 9, and a blowing experiment was conducted.

Since the bath shakes extremely violently during blowing, the crucible must be
It was necessary to cover the lid 10 to prevent the molten iron from scattering. In the experiment, varying ratios of oxygen and coolant water were blown into the bath, and at the same time, the generated dust was sucked onto the bath, and the absolute amount of dust and Fe value in the dust were analyzed.

The basic requirement from these experiments was to form water into fine droplets in the oxygen flow path in advance and to distribute it uniformly in the oxygen flow. In other words, when the water that is blown into the bath is not atomized and flows along the inner pipe wall as a fluid and enters the bath, abnormal vibrations occur within the bath, making it impossible to blow into the bath. There was also a risk that the nozzle tip would become clogged.

Embodiment 1 FIG. 2 shows an example of a flow when water is atomized in an oxygen flow path when oxygen or an oxygen-containing gas is blown into an iron bath. In the flow shown in the figure, oxygen or oxygen-containing gas is blown into the iron bath 4 from the pipe 3 through the gas nozzle l. At this time, a constriction section 5a shown in FIG. 3 is provided in the flow path so as to maintain a flow velocity of 30 m/sec or more. A high flow rate part 5 was provided, and the water sent from the water head tank 6 through the water supply pipe 7 was atomized in the form of a mist, and the fine water droplets generated here were sent to the nozzle 1 to try to cool the nozzle. . As a result, stable operating conditions were obtained.

FIG. 4 shows the results, and it can be seen that as the H,0\ (mol)10x (mol) ratio on the horizontal axis increases, the duct amount decreases significantly.

In addition, when a gas nozzle 2 indicated by the broken line in FIG. 2 was added and the nozzle was branched into two and a blowing experiment was conducted, even better blowing conditions were obtained.

Prior to this experiment, we conducted a cold model test to observe how the water distribution situation changes depending on the presence or absence of an atomization device. If there is no atomization device, the water will flow unevenly along the pipe wall due to insufficient atomization, and in the case of multiple nozzles, the amount of water distributed by the nozzles will be different, leading to inappropriate results such as excessive flow to one nozzle. Ta. It is clear that problems will occur if atomization is inappropriate even with a single nozzle, and it is clear that making water into fine particles is extremely important.

Example 2 Using the iron bath furnace shown in FIG. 1, an attempt was made to atomize by injecting pressurized water into an oxygen pipe (10 m/5 ec) at a normal flow rate through a syringe needle.

In this case, the pressure difference between the pressure just before the water nozzle (in this case, the pressure in front of the syringe needle) and the pressure inside the oxygen tube is important, and a pressure difference of at least 0.3 kg/c1i1 or more is required; if it is less than that, atomization will not occur. It was found that the water flow was not sufficient and the water flowed on the inner wall of the pipe, causing the water amount to be distributed unevenly by the distributor. 0.3
In the case of a pressure difference of 1 kg/cff1 or more, preferably 1) cg/cff1 or more, water droplets become sufficiently thin and are distributed evenly to each nozzle along with the air flow. In this case, the pressure inside the oxygen tube changes depending on the oxygen flow rate and the situation in the bath, so a control device is required to follow it.

Example 3 In Example 1.2, the immersion nozzle was used from above, but in Example 3, a short pipe nozzle 1a was installed at the bottom of the furnace 8a as shown in Fig. 5, and a 40 kg iron bath was poured. A test was conducted in which oxygen was blown into the tank. In the case of bottom blowing shown in FIG. 5, the nozzle gas flow velocity is required to have a value close to the sonic velocity in order to avoid attack by the molten iron 9. Therefore, the nozzle body la
We thought about atomizing the cooling water by using the dynamic pressure of the gas (often oxygen) passing through it, and tried that. That is, by installing the injection needle 7a in the center of the oxygen flow pipe 3a and flowing water at 70 g/Nrrf Oz, it was possible to operate the bottom blow nozzle and the furnace bottom brick without any trouble. Note that 11 in the figure is a dust sampling tube.

Note that the methods of Examples 1 to 3 can be similarly applied to a nozzle that blows from the side below the bath surface.

The above examples of atomizing water have been shown, but these methods can be used in two ways.
A combination of two or more may be used for atomization at the same time, and methods other than those shown above may be similarly applied as long as they can sufficiently atomize water.

(Effects of the Invention) As explained above, the method of the present invention can lower the temperature at the tip of the nozzle by directly spraying water into the airflow of the acid supply nozzle, protect the nozzle, simplify the nozzle, and reduce the It has become possible to achieve an improvement in yield due to the decrease in

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing an example of an iron bath furnace used to carry out the present invention, Fig. 2 is a flow diagram showing an example of atomizing water according to the present invention, and Fig. 3 is Fig. 2 FIG. 4 is a diagram showing the relationship between the amount of coolant and dust I for detailed explanation of the present invention, and FIG. It is a longitudinal cross-sectional view which shows another Example of a furnace. 1.1a12... Gas nozzle, 3... Piping for oxygen supply, 4.9... Iron bath, 5... High flow rate section, 5a... Throttle section, 6... Head tank for water , 7... Water supply pipe, 7
a... Water supply syringe needle, 8... Crucible, 8a... Furnace body, 1o... Lid, 11... Dust sampling tube,
12...Electric heating agent Patent attorney Masa Akizawa Mitsuru A9 / Thread 71 Figure 5α

Claims (1)

[Claims] 1. In a method of supplying oxygen or an oxygen-containing gas into molten metal through a gas nozzle disposed below the bath surface of a molten metal furnace to cause a chemical reaction accompanied by heat to occur, A method for cooling a gas nozzle of a molten metal furnace, characterized in that the atomized state is suspended in oxygen or an oxygen-containing gas and supplied to the gas nozzle. 2.In the oxygen or oxygen-containing gas flow path behind the nozzle, provide a gas high flow rate section of 30 m/sec or more, and inject water from the nozzle into this high flow speed section, or in the oxygen or oxygen-containing gas flow path behind the nozzle. A water injection nozzle is provided through the pipe wall, and water is injected from the nozzle with a pressure difference between the pressure immediately before the water nozzle and the gas pressure of oxygen or oxygen-containing gas at 0.3 kg/cm^2 or more, or Alternatively, water is atomized by spraying water from a water jet nozzle provided in the high-flow velocity part of the bottom-blowing nozzle body and utilizing the dynamic pressure of high-flow airflow, either alone or in combination of two or more. 1. The method for cooling a gas nozzle of a molten metal furnace according to 1.