JPH0469575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and an apparatus for adding a component adjusting material into an electric furnace for heating blast furnace molten slag, which is a raw material for rock wool.

[Conventional technology]

Inorganic fibers called mineral wool, slag wool, rock wool, etc. are also manufactured by melting natural rocks and making them into cotton, but in Japan, they are most commonly made by adding composition adjustment materials to crushed blast furnace slag as necessary. It is added and remelted in a melting furnace such as an electric furnace or a cupola, and the molten material is fed to a cotton machine where centrifugal force and/or
Alternatively, a method of forming fibers using fluid pressure such as compressed air or steam has been adopted. This conventional method uses crushed slag stone, so it is convenient for transportation and storage of raw materials, and the raw materials themselves, such as silica stone and dolomite, which are added to adjust chemical components, are crushed stones, so they are mixed and melted at the same time. Even if there were problems with uniform mixing of solids, there were relatively few problems due to the large volume of the furnace and the long residence time.
Above all, the huge amount of heat taken out of the blast furnace is released when it is left to cool, resulting in it being unusable and being discarded.

Therefore, from the viewpoint of energy conservation, attention is being paid to a method in which high-temperature molten slag from a blast furnace is directly charged into an electric furnace, the composition and temperature are adjusted in the electric furnace, and then the slag is supplied to a cotton milling machine. For example, it is described in Japanese Patent Publication No. 37-4559 as a method for producing high slag cotton. Tokko Akira
Publication No. 59-131534 and the like have exactly the same technical content. In these methods, the energy consumption is only required to slightly heat the molten slag in an electric furnace and melt the composition adjusting material such as silica stone, so a large amount of energy can be saved compared to conventional methods. However, the slag discharge from the blast furnace is performed intermittently every few hours, and the molten slag transported by ladle truck must also be charged intermittently into the electric furnace. on the other hand,
In order to stabilize the quality of rock wool and improve the yield, it is important to minimize fluctuations in the composition and amount of melt fed to the cotton mill.

When a slag melt cooled during transport is added to a raw material melt which is a suitable constituent for rock wool cotton, non-uniformities in composition and temperature occur. In order to adjust the components, a preheated component adjusting material such as silica stone is usually poured onto the bath surface from above. Even if this component adjusting material is preheated, the temperature is much lower than the bath temperature, so there is a problem that it hardens together on the bath surface and does not melt uniformly.

Although it is not a solution to this problem, as a means to protect the furnace wall carbon bricks of a melting furnace,
Publication No. 113335 states that neutral or reducing bubble gas is blown into the bath from the bottom of the electric furnace or through the electrodes to make the bath homogeneous, and that a dust-reducing additive such as charcoal or petroleum coke is added to the bath together with the bubble gas. It is described that a reducing atmosphere is created within the furnace enclosure by blowing into the furnace enclosure.

[Problem that the invention seeks to solve]

Incidentally, the addition of the composition adjusting material to the electric furnace is particularly necessary for composition adjustment when the slag melt cooled during transportation is injected into the raw material melt in the melting furnace. However, at this time the temperature of the bath, especially the upper part of the bath, has dropped due to the injection of the slag melt. Even if it is preheated, if you charge the composition adjustment material below 400℃ from above, even if you charge it in powder form that is easy to melt, it will solidify together in the bath, and it will be difficult to dissolve it uniformly even if you stir it. The problem was that it didn't.

[Means for Solving the Problems] The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, they have devised a method for introducing inert gas through a lance pipe inserted into the bath through the furnace lid. The present inventors have discovered that by stirring the molten bath by blowing air into the bath, and adding powder of the component adjusting material into the bath along with this inert gas flow, the component adjusting material can be uniformly dissolved in the bath in a short time. completed.

That is, the present invention involves adding a component adjusting material into a melt bath along with an inert gas flow through a vertically movable lance tube inserted into an electric furnace for heating a slag melt while sealing the furnace gas. This is a method for adding a component adjusting agent to a slag melt, characterized by the following. The apparatus for carrying out this method includes a lance tube that penetrates the electric furnace lid through a gas sealing device and a gate valve, and whose lower end is inserted into the molten material in the furnace and is movable up and down. A method for adding components to a slag melt by connecting an active gas conduit through a flexible tube and connecting a component adjusting material supply device to any of the upper parts of the inert gas conduit, flexible tube, and lance tube. This is an adjustment material addition device.

To carry out the method of the present invention, it is necessary to stir the molten bath in the electric furnace by blowing inert gas such as nitrogen gas or argon gas through a lance tube inserted into the bath through the furnace lid. be. Melting bath is 1500℃
Since the temperature is high, carbonaceous materials such as graphite or silicon carbide refractories are used for the refractory lining of the furnace. Since the molten bath is mainly composed of highly basic blast furnace slag, ordinary oxide-based refractory materials cannot be used because they are susceptible to corrosion. Carbon or silicon carbide refractories have less wettability to slag and less corrosion. However, this type of refractory has the disadvantage of being oxidized and consumed at high temperatures in the presence of oxygen. Therefore, the space inside the furnace is filled with an inert gas such as nitrogen gas and maintained at a positive pressure to prevent air from entering. Gas injection lance pipe,
For the same reason, at least the portion immersed in the melt bath is made of carbon or silicon carbide refractory material. As shown in FIG. 2, this lance tube 1 is preferably inserted within the circumscribed circles of three circles when the electrode 13 is considered to be tight at the melt level. this is,
This is because this is the area where the current density is the highest, the temperature is the highest, and the viscosity of the bath is the lowest. In particular, the lance tube 1 is made of a conductive material such as carbon or silicon carbide, and the reference numeral 1 in FIG.
When the bath is inserted at the midpoint on the line connecting the electrodes 13 as shown in FIG. The low-viscosity melt heated by this gas injection rises, reaches the bath surface, flows toward the furnace wall, becomes a downward flow near the furnace wall, and convective stirring and convective heat transfer occur.

If this lance tube is immersed too shallowly, the blowing gas will have little effect on moving the molten material.On the other hand, if it is too deep, it will not only be out of the heating zone by the electrode and unable to blow into the lowest viscosity area, but also The inner lance tube also becomes longer, increasing the risk of the lance tube breaking. Therefore, the lance tube is held by a support member outside the furnace so as to be able to move up and down. This lance tube is equipped with a gas seal device to prevent inert gas from leaking inside the furnace.
It passes through the furnace lid through the gate valve. In this way, while sealing the gas in the furnace, inert gas for bath stirring is flowed through the lance tube inserted into the furnace, and powdered composition adjusting materials such as silica powder are suspended in this gas flow, and the mixture is bathed together with the gas. Send it inside. The particle size of the silica powder is preferably 5 mm or less, preferably 2 mm or less so that it can be suspended in the gas. The gas flow rate is 5 m/sec or more, preferably 10 m/sec or more.

The particle size of the conditioning material is adjusted by the flow rate of the stirring gas. That is, if the flow rate is low, the particle size is also fine. The gas in the furnace is, of course, discharged to the outside through the discharge port while maintaining a constant positive pressure. The component adjustment material is preheated by combustion gas, etc., and after being weighed, it is stored in a hopper.
It is fed into the inert gas by a metering device at the bottom of the hopper. Another method is to blow circulating gas from the bottom of the hopper to create a fluidized bed of the conditioning material inside the hopper, and use a portion of this fluidized bed to suck the conditioning material through the ejector effect of an inert gas, causing it to flow into the gas. You may also do so.

In an apparatus for carrying out the method of the present invention, in order to move the lance tube up and down, a flexible tube is connected to the upper end of the lance tube, and the flexible tube is connected to an inert gas conduit. The lance tube's passage through the furnace cover is designed to seal the furnace gas when it is pulled out and inserted to replace the lance tube, and also to seal the furnace gas at all times.
Gas seal devices such as gland seals or mechanical seals and gate valves such as slide gate valves,
For example, (seal device) - (gate valve) - (seal device)
Install with this combination.

As for the vertical movement mechanism, the upper part of the lance tube is held so that it can slide on a support member or can be rolled by a guide wheel, and the guide wheel is moved up and down by a wire or chain and a drive motor that drives it, or The vehicle may be moved up and down by a rack and pinion mechanism.

The conduit from the component adjusting material supply device may be connected to any of the inert gas conduit, the flexible tube, or the upper part of the lance tube. Although an inert gas conduit is advantageous in that the tube is fixed, when connected to an inert gas conduit or flexible tube, the inert gas flow typically fluidizes the conditioning powder and moves it upward. Creates a part to lift. In this case, the gas flow rate is determined by the above-mentioned stirring gas amount and the inner diameter of the conduit, which determines the maximum particle size that can be fluidized and lifted. On the other hand, when connected to the upper part of the lance pipe, it moves up and down, so the connecting conduit must be connected with an expandable pipe, but even if the particle size of the adjusting material is large compared to the gas flow rate, it will not fall due to gravity. can be fed into the furnace by That is, there is an advantage that there is no restriction on the particle size of the adjusting material depending on the amount of gas. In this case, the component adjustment material storage hopper should be located sufficiently higher than the lance pipe, and there should be no rising part between the hopper and the lance pipe, and a telescopic pipe consisting of an inner and outer double pipe should be used so that it descends unilaterally. A device such as is preferred.

〔Example〕

Next, an embodiment of the apparatus according to the present invention will be described with reference to the drawings. Figure 1 shows that the means for moving the lance tube up and down is a rolling system of a guide wheel relative to the support member, and the drive is performed by a wire and a motor with a speed reducer, and the adjustment material is added through an inert gas conduit. This is the case. 1 is a carbonaceous lance tube, and if necessary, only the portion that enters the furnace may be a graphite tube, and the upper portion may be a metal tube. 2 is a flexible tube made of rubber, synthetic resin, or metal, and corresponds to the vertical movement of the carbonaceous lance tube 1. 3 is an inert gas conduit, 4 is a guide wheel for the carbonaceous lance tube 1, and 5 is a rolling wheel thereof. 6 is a support member for the carbonaceous lance tube 1, and the guide wheel 4 is supported by this support member 6 via a rolling wheel 5. The guide wheel 4 includes a wire 7 and a motor 8 with a reduction gear.
Driven by. 12 is an electric furnace, and the carbonaceous lance tube 1 has a gas sealing device 9,
10 and a gate valve 11 to seal the gas inside the furnace. After the component adjustment material 15 is weighed and preheated,
It is stored in the component adjustment material storage hopper 14. This amount is determined in accordance with the amount of molten slag charged into the electric furnace 12. The component adjusting material 15 is added little by little to the inert gas stream by the quantitative feeder 6, fluidized, and charged into the furnace together with the inert gas during melting.

In Fig. 3, the support member also serves as a rack gear, a motor with a reduction gear and a pinion gear driven by this are mounted on the guide wheel, and the lance tube is driven by the rack and pinion mechanism, and the composition adjustment material is applied to the lance tube. This is an example in which the adjustment material is merged with inert gas at the upper part of the guide wheel, and sent into the furnace together with the gas using gravity through a telescoping tube. 18 is a rack gear, which also serves as a support member. 19 is a pinion gear that moves the carbonaceous lance tube 1 up and down. 1
Reference numeral 7 denotes an extensible tube consisting of an inner and outer double tube, and the upper part is sealed to prevent gas from leaking. In the case of this embodiment, the rack gear 18 and the component adjustment material storage hopper 14 are installed integrally with the electric furnace 12, and the upper end of the component adjustment material storage hopper 14 is connected to the preheater with a swivel joint or other flexible tube. This allows the rack gear 18 and the component adjustment material storage hopper to follow the tilting movement of the electric furnace 12.

Next, an example in which the above device is used will be described.

5 tons of blast furnace molten slag is charged into the rock wool raw material melt in an electric furnace, nitrogen gas is blown through a graphite lance tube inserted from the furnace lid, and the molten bath is pulverized to a particle size of 2 mm or less while stirring. After weighing
500 kg of silica powder preheated to 350°C was added at a rate of 25 kg/min while floating in a nitrogen gas flow and fed into the furnace. As a result, in the case of the conventional method in which silica powder was added to the bath surface all at once, it took more than 40 minutes for complete dissolution, and undissolved lumps caused electrode breakage and furnace wall damage. In the examples, almost complete dissolution was observed upon charging.

〔effect〕

The rock wool raw material melt in the electric furnace is continuously discharged to the cotton mill, and when the raw material in the furnace reaches a certain amount or less, blast furnace molten slag is charged. At this time, since the slag temperature is lowered due to transportation, the bath temperature is lowered. If preheated but below 400℃ component adjustment materials are added to the bath surface all at once, they will solidify together and form lumps, which will take a long time to completely dissolve, and these lumps will cause electrode breakage and furnace wall damage. However, according to the present invention, by adding the component adjustment material little by little together with the stirring gas, the component is completely dissolved at the same time as the addition, and no lumps are formed. Not only was it possible to uniformly adjust the temperature, but the causes of electrode breakage and furnace wall damage were also eliminated.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional view showing an embodiment of the device for adding composition adjusting material to molten slag according to the present invention, Fig. 2 is a horizontal sectional view showing the optimal lance tube insertion point between the electrodes, and Fig. 3 is FIG. 3 is a vertical cross-sectional view showing another embodiment of the device for adding a component adjusting material to a slag melt according to the present invention. 1... Carbonaceous lance tube, 2... Flexible tube, 3...
...Inert gas conduit, 9...Gas seal device, 10
...Gas seal device, 11...Gate valve, 12...
Electric furnace, 14...Component adjustment material storage hopper, 15
...Component adjustment material, 16...Quantitative supply device.

Claims (1)

[Claims] 1. A component adjusting material is added into the melt bath along with an inert gas flow through a vertically movable lance tube inserted into an electric furnace for heating the slag melt while sealing the furnace gas. A method for adding a composition adjusting agent to a slag melt, characterized by: 2 At the electric furnace lid, an inert gas conduit is passed through the furnace lid through a gas sealing device and a gate valve, and an inert gas conduit is inserted into a vertically movable lance tube whose lower end is inserted into the melt in the furnace. A device for adding a component adjusting material to a molten slag, which is connected to the inert gas conduit, the flexible tube, or the upper part of the lance tube. 3. An apparatus for adding a composition adjusting material to a molten slag according to claim 2, wherein the composition adjusting material supplying apparatus is provided with a quantitative feeding apparatus at the lower end of a composition adjusting material storage hopper.