JPS61149416A - Pretreatment of molten pig iron - Google Patents

Abstract

PURPOSE:To prerefine easily molten pig iron by bringing the tip of an evacuated movable pipe close to slag on the molten pig iron flowing in spout to remove the slag by the sucking force. CONSTITUTION:Molten pig iron 40 is discharged from a blast furnace into a spout 42, blast furnace slag is removed with a skimmer, and the flow is regulated. A desiliconizing agent is then blown into the molten pig iron 40 together with gaseous N2 from a lance 46. The desiliconizing agent reacts with the molten pig iron 40, forming and floating slag. This slag is sucked by the sucking pipe 33 of a movable slag sucking device 30, and the desiliconized molten pig iron is poured in a torpedo car through an inclined spout 50.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for pretreatment of hot metal, in particular a method for pretreatment of hot metal in a tap runner connecting a so-called blast furnace and a suitable pig iron receiving vessel.

(Prior art) The importance or necessity of pre-treatment of hot metal in the tap hole that receives hot metal from the blast furnace has been recognized in recent years due to modern objectives such as reducing the load on the converter and improving productivity. Gender is beginning to be recognized. However, as a method for removing sludge following such preliminary treatment, Japanese Patent Laid-Open No. 54
-137420, etc., a separation wall (hereinafter simply referred to as a "skinmer") is installed to prevent the slag on the hot metal from flowing out, and a slag trough with an overflow set is installed in the slag pool upstream of the wall to prevent the slag from flowing out. It was common. but,
This one-type skimmer had structural problems because it required a sufficient depth at the dam of the hot metal trough and a sufficient length to form a slag pool.

On the other hand, as a method of removing the slag in the next step, which is the pig-mixing car, without removing the slag on the tap runner, there is a method called
Slag scraping device such as No. 3 and Special Publication No. 58-41435
Vacuum suction sludge removal devices such as No. 1 are known. However, both methods require work inside a pig iron mixer car, and require one step to treat the slag, resulting in extra costs in terms of time and work. In addition, a lot of hot metal flows out at the same time as slag scraping, resulting in poor yield (f4 pig iron yield).
Furthermore, the efficiency of suction slag removal is greatly affected by the properties of the slag, and it is necessary to take measures to improve the fluidity of the slag in response to a decrease in temperature, as seen in Japanese Patent Publication No. 58-38484.

On the other hand, installing a vacuum suction device above the hot metal gutter requires a water treatment device under vacuum with conventional devices (injecting water and suctioning slag into a slurry), which requires a lot of equipment and space for installation. It was impractical in terms of target and equipment cost.

- (Problems to be solved by the invention) As mentioned above, at present, during preliminary refining in the tap sluice of an existing blast furnace, the molten pig iron after refining is received into the pig iron mixer car together with slag, and then the hot metal is transferred into the pig iron mixer car. The slag is removed by a mechanical slag removal method such as a slag dragger, a slag removal method using a vacuum slag remover, or the like. Therefore, even though preliminary refining is carried out in the tap runner, the subsequent refining is often carried out in the pig iron mixer car.The disadvantage of this method is that the refining time in the pig iron mixer car is extra. This means that during this time, the temperature drop due to the time required for slag removal and refining, etc., has a considerable influence on subsequent steps.

(Means for Solving the Problems) The object of the present invention is to provide a simple method for removing slag that can easily pre-smelt hot metal even if it is in the tap trough of an existing blast furnace. An object of the present invention is to provide a method for pretreatment of hot metal.

Another object of the present invention is to provide a method for pre-treatment of hot metal, which makes it possible to easily incorporate the necessary slag removal process into an existing blast furnace when continuously refining in the tap culvert from the blast furnace. It is to be.

That is, the present invention is a hot metal pretreatment method characterized in that the tip of a depressurized movable tube is brought close to the slag above the hot metal flowing in the gutter, and the slag is removed by the suction force. This method uses a reduced pressure suction system and the suction nozzle is movable, so the slag removal device can be easily installed in the tap trough from an existing blast furnace. Note that the tapping trough here also includes a tilting trough that changes the direction of the flow of hot metal.

More specifically, the gist of the present invention is to add a refining agent to the hot metal flowing through the tap hole, which receives hot metal from a blast furnace at one end and injects it into a receiving container from the other end. The hot metal pretreatment method is characterized in that floating slag generated by adding the refining agent is removed by suction from the surface of the hot metal by bringing the tip of a suction nozzle close to the surface of the hot metal at an appropriate position in the tap flue. .

The decompression slag removing device equipped with a movable nozzle tip on the tap runner is the device disclosed in Japanese Patent Application No. 164629/1983, which sucks and removes the slag floating at the top of the hot metal flow after addition of the refining agent. It is.

In particular, in hot metal desiliconization treatment, as long as the desiliconizing agent and hot metal are well mixed, the desiliconizing reaction is extremely fast. 8 of slag removal by suctioning the floating slag at the
More than 0% can be removed.

As you can see, the method of suctioning and removing slag using a reduced pressure pipe is often adopted when removing slag from molten steel or pig iron mixers. It is possible to suction remove only the area around radius "a". (“a” varies depending on the vacuum pressure, slag properties, distance between the slag and the vacuum pipe, etc.). Here, "a" is approximately 1 m according to the experimental results of the present inventors.
Within On the other hand, the slag surface inside the molten steel or pig iron mixer car often has a length of 5 to 10 m. Therefore, in order to remove the molten steel and slag in the pig iron car by suction, it becomes necessary to use another device to stir up other slag around the suction pipe or to move the suction pipe of the pressure reducing pipe.

However, in the method of the present invention, since the width of the blast furnace gutter is usually within 1 m, it is not necessary to move the pressure reducing pipe described above in the width direction of the gutter, and by simply moving it close to the bridge, the entire width of the gutter can be increased. It is easy to cross and remove slag. However, due to changes in the hot metal flow rate and changes in the amount of refining agent added, the optimal suction position downstream of the refining agent injection position changes.
It is preferable that the slag removal suction pipe be movable with respect to the flow direction of the hot metal.

As described above, the sludge removing device is not particularly limited to a vacuum suction type, a single ejector type, etc., but a dry type one ejector type is preferred from a practical point of view.

As for the method of adding the desiliconizing agent, the injection method from the top using high pressure gas is most preferable in terms of the mixing rate (mixing rate per hour) and the stirring surface of the hot metal, and the reaction time can also be shortened.

If the tap runner is long enough, the slag produced in the next stage of treatment (for example, dephosphorization) can be sucked in as well, but in general, dephosphorization and desulfurization reactions are slower than desulfurization reactions. Since the treatment agent is also expensive, it is necessary to allow sufficient reaction time and to perform mixing, so removal by suction on the tap trough is not necessarily advantageous. However, if a soda ash-based refining agent with an extremely fast reaction rate is used, dephosphorization,
The desulfurization reaction reaches its highest efficiency at around 10 seconds, and after that the efficiency decreases due to rephosphorization and resulfurization. It is preferable to carry out the slag removal of the present invention.

In addition, even without continuous treatment on the tap runner, the amount of slag is extremely reduced compared to the conventional case where all desulfurization slag is put into the mixer car. It has the advantage of reducing the amount of molten pig iron in the pig iron mixing car (reactions and slag blowing), increasing process efficiency, and reducing the cost of forming inhibitors.

(Operation) Next, the present invention will be explained in more detail with reference to the accompanying drawings.

Among the accompanying drawings, FIG. 1 is a flowchart of the treatment steps from blast furnace tapping to converter when the hot metal pretreatment method according to the present invention is utilized. Figure 2 shows the same (conventional).

That is, according to the present invention, the blast furnace slag is first removed from the hot metal from the blast furnace by a skimmer on the tap trough, and then, according to the present invention, a refining agent is introduced into the hot metal flow, that is, a desulfurization treatment and suction slag removal are performed. .

When the desulfurization treatment and slag removal are completed, a dephosphorizing agent is added to perform dephosphorization. Generally, the dephosphorization reaction progresses slowly, so the reaction does not complete on the tap runner, and therefore slag removal is not performed. Hot metal is injected together with a dephosphorizing agent into a pig iron mixer through a tilting culvert.In this case, if a sufficient reaction is not obtained on the bridge, or if it is difficult to remove the slag from the torpedo due to poor slag formation,
The hot metal is stirred by injection etc. in the pig iron mixing car.
At the same time as dephosphorization, the original properties are improved, and then torpedo removal is performed to remove the dephosphorization slag. After dephosphorization, the hot metal is transferred to a ladle,
The remainder of the dephosphorization slag is scraped out, and then a desulfurization agent is added to perform desulfurization.

In the example of the present invention shown in FIG. 1, blast furnace slag is first removed by a skimmer in order to perform a kind of rectification effect.

In the conventional example shown in FIG. 2, only the desulfurization agent is added in the tap runner, and the desulfurization slag is removed as torpedo slag. Although the desulfurization reaction itself occurs quickly, this is because there was no means to quickly remove the product on the tap runner.

FIG. 3 shows a slag suction device 30 used in the present invention.
It is a schematic explanatory diagram of gutter refining using the pressure gas (2 kg/cn
1 or more), the slag 34 is suctioned from the suction pipe 33 by the suction force generated by the negative pressure generated by the suction tube 33. The suctioned slag is discharged from the outlet of the pressure reducing pipe 31 and is usually collected by a dust collector (not shown).

The blowing position of the pressure tube 32 is normally preferably a portion directly above the center of the suction tube 33, where the suction force is strongest. In addition, in the case of adhesive slag, such as desulfurization slag, the water injection pipe 3
By pouring water from 5, it is possible to prevent slag from adhering to the suction pipe. Alternatively, it is also possible to add lime powder to change the slag properties during suction.

The suction tube 33 need not be vertical, but may be tilted relative to the scene. In this case, the suction force does not decrease, but the amount of slag suction is slightly affected by the tube wall resistance.

The relationship between the pressure of the pressure gas body, the diameter of the pressure reducing pipe 31 and suction pipe 33, and the distance between the end face of the suction pipe 33 and the slag surface varies greatly depending on the slag properties, so it must be confirmed experimentally, but ultimately It can be controlled by the pressure of the pressure gas and the distance between the slag surface and the suction pipe 33. As already mentioned, in accordance with the present invention in FIG. 3, hot metal 40 from the blast furnace is first subjected to a conventional skimmer 44 before being tapped into the tap runner 42 and injected into the mixer car. Blast furnace slag is removed and rectified. Next, an appropriate refining agent, such as a desulfurizing agent, is blown into the hot metal together with N2 gas through a lance 46. The desulfurizing agent immediately reacts with the hot metal to form slag, which is suspended. This produced slag 48 is then sucked by the slag suction device 30, and after further adding a dephosphorizing agent if necessary, it is injected into a pig iron mixer (not shown) via a tilting trough 50.

Next, the present invention will be explained in further detail with reference to Examples.

EXAMPLE A hot metal pretreatment apparatus similar to that shown in FIG. 3 was used to preliminarily refine hot metal tapped from a blast furnace.

Processing conditions and equipment dimensions are summarized in the table below.

Table According to the present invention, the Si content of the hot metal which was 0.50% when the blast furnace slag was removed by the skimmer 44 decreased to 0.13% Si after the desiliconization slag was removed. The silica rate is 74%. The generated slag removal point was 1 m downstream from the point where the desiliconizing agent was introduced.

(Effects) Thus, according to the present invention, by installing the slag removal pipe 1 m or more downstream from the point at which the desiliconizing agent is added, the slag after the refining reaction can be removed by suction. You can enter.

The slag after dephosphorization can be removed at the gutter nose or the tilting gutter, but it may be removed at any point after the refining reaction is completed.

Therefore, according to the present invention, the hot metal is processed while flowing on the tap tap, so the method according to the present invention does not add any new process time.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of a hot metal pretreatment method using the method of the present invention; FIG. 2 is a flowchart of the conventional method; and FIG. 3 is a schematic explanatory diagram of gutter refining. 30 Nisslag suction device 31: Pressure reducing pipe 32: Pressure pipe 33: Suction pipe 34 Varnish slag 35; Water injection spray pipe 40: Pig capacity 42: Tapping sluice 44 Niss slag 46 Second lance 48: Generated slag Applicant Agent Sumitomo Metal Industries, Ltd. Person Patent Attorney Akira Hirose - (1 person) 10 to ψ ro++;r size cough Kayan Of- to rO rOr'OrOr0

Claims (3)

[Claims] (1) A refining agent is added to the hot metal flowing through the tap trough, which receives hot metal from the blast furnace at one end and injects it into the receiving vessel from the other end, and floating slag is generated by the addition of the refining agent. A hot metal pretreatment method characterized in that the suction nozzle tip is brought close to the surface of the hot metal at an appropriate position of the tap duct to remove the hot metal by suction from the surface of the hot metal. (2) The hot metal pretreatment method according to claim 1, wherein a dephosphorizing agent is added as the refining agent, and the generated floating slag is removed by suction from the surface of the hot metal, and then the dephosphorizing agent is added. (3) The hot metal pretreatment method according to claim 1 or 2, wherein the tip of the suction nozzle is movable.