JPH09263817A - Method for killing slag foaming at the time of melting molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize sludge containing oil content as a slag foaming killing agent. SOLUTION: The sludge 2 containing the oil is precipitated in a sludge collecting vessel 1 and separated from the water 21 and once carried to a holding pond 6, and after dehydrating, the sludge is piled in solar drying field 7 and naturally dried with the solar energy to make dry sludge 20 containing the oil having <=40wt.% moisture. The dry sludge 20 containing the oil is discharged from a carriage hopper 22 and charged into a foaming slag 15 floated up on desiliconized molten iron 10 in a torpedo car 11 and slag foaming is quickly killed with the foaming killed action by gasifying the oil content. The sludge 2 containing the oil can be reused at a low cost by so extremely simple method as to naturally dry this sludge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when melting steel or other metal as a molten metal, suppresses slag foaming during forming in a container that receives the molten metal, so that oil-containing sludge is formed into a calming agent. The present invention relates to a slag foaming method for soothing molten metal that can be used as a resource.

[0002]

2. Description of the Related Art As molten metal, a large amount of impurity elements such as Si, P, and S is contained in molten pig iron produced in a blast furnace. It will greatly affect the refining efficiency and steel quality in the steelmaking process such as. Therefore, in general, in order to remove the impurity elements in the hot metal, prior to the steelmaking process, desiliconization, dephosphorization, and
Hot metal pretreatment such as desulfurization is performed to reduce the amount of auxiliary raw materials such as lime used in the steelmaking process to facilitate the production of molten steel.

[0003] Conventionally, hot metal pretreatment for spraying powdered granular flux or soda ash, which is a mixture of iron ore, mill scale, etc., with lime, fluorite, etc., together with the carrier gas, or for blowing it into the hot metal. The method is known.
For example, the hot metal that flows through the hot metal gutter installed in the blast furnace casting floor is guided to a downspout, and a desiliconizing agent (desiliconization flux) is sprayed onto the hot metal in this downspout to desiliconize the hot metal with a tope car. Accept. In this case, if the viscosity of the slag floating on the hot metal received by the hot metal is large, CO and CO ₂ gas generated from the hot metal causes the slag to foam and expand, and overflows from the hot metal. This not only makes it difficult to receive the hot metal in the toped car, but also causes a large problem such as the molten slag being deposited on the track on which the toped car runs, which impedes the running of the toped car. Foaming due to such volume expansion of the slag is called a forming phenomenon, but for this reason, it causes disadvantages such as insufficient cast bed desiliconization or having to keep the pig iron amount of the tope car low. It will be.

Further, such a forming phenomenon similarly occurs when molten steel is melted in a converter or an electric furnace, which is a problem. When molten steel is produced by converter blowing, slag foaming occurs in the furnace at the end of blowing, and particularly at the end of blowing low carbon steel, the slag remarkably foams and expands. Such a slag forming phenomenon varies in degree depending on the viscosity of the slag and the steel type, but CO gas or the like generated in the molten steel cannot be released from the highly viscous slag, and becomes bubbles and is trapped in the slag. It exists and gradually swells. When such slag forming occurs, the temperature of molten steel cannot be measured or sampled, and in order to wait for the forming to subside, not only is the operating rate of the converter reduced, but it is also necessary to re-blown the converter. It will be. If the steel is tapped without sufficiently calming the slag foaming, the slag foams in the ladle and there is a risk that it will overflow, which is a major safety issue.

The cause of the forming phenomenon is CO or C produced by the reaction between carbon and oxygen in the hot metal or molten steel.
This is because the O ₂ gas bubbles up and pushes up the slag, because the O ₂ gas is not sufficiently diffused outside the container by being disturbed by the slag floating on the molten metal surface. Therefore, in order to suppress or prevent the forming phenomenon, the slag layer on the molten metal surface may be broken by some means, and the fluidity of the slag layer may be improved to remove CO and CO ₂ gas. Therefore, in the above-mentioned topped car that receives desiliconized hot metal in the cast bed, wetting river sand or water in the hope of removing the slag layer due to the rapid generation of steam, or improving the fluidity by combustion. There was a case where chaff was added to the slag in anticipation of the above, but there is little effect, or even if there is an effect, there is a danger of a steam explosion, and it is no longer implemented.

Further, in the converter, the forming sedative has been improved for a long time.
40 wt%, the balance being _{MgO, CaO, SiO 2, Al} 2 O 3, FeO of one or more mixture or forming sedative made of an inorganic compound which is a compound (JP-B 50-6406 JP) Forming sedative consisting of 40-60% by weight of converter slag, 30-40% by weight of sawdust, and 5-30% by weight of water (JP-A-52-115716), blast furnace dust that collects blast furnace exhaust gas and blast furnace water granulation 90% by weight or less and waste oil at 12% by weight or less, a forming sedative (Japanese Patent Laid-Open No. 53-40614), dust, sludge, mill scale, powder ore, sinter ore powder It is disclosed that a forming sedative formed by adding a surfactant and a binder to a raw material containing at least one kind and containing an oil (Japanese Unexamined Patent Publication No. 60-230928) is added.

However, although the one disclosed in the above publication effectively uses waste such as converter slag, sawdust, dust collecting dust and sludge as an inexpensive raw material,
Its production is troublesome and too expensive to use in large quantities. On the other hand, at steel mills, those that contain 2 to 25% oil, such as sludge generated from slab mills and rolling mills, and sludge generated in the direct cooling system of slabs in continuous casting equipment installed in steelmaking plants. Occurs. Such sludge is generally used as follows in order to recycle oil-containing sludge as a raw material for iron production because of its high iron content.

(1) Although it was often cycled as a raw material for sinter, the oil was volatilized in the sinter and accumulated in the dust collector and spontaneously ignited by the high temperature atmosphere, causing the dust collector to burn out. Cause to invite. Because of this, oil has recently been
It is limited to sludge with an extremely low oil content of less than 10%, and the sludge with a high oil content containing 10 to 25% by weight of the above-mentioned sludge cannot be reused.

(2) In some cases, the oil content in the oil-containing sludge is incinerated, granulated and reduced, and charged as pellets into the blast furnace.
The construction and operation of the equipment for this purpose not only requires a great deal of cost, but also has the drawback of causing environmental problems including air pollution accompanying combustion. (3) When oil-containing sludge is made into briquettes and then sintered at a high temperature and charged into a blast furnace or converter, or when briquettes molded by a briquette molding machine are directly charged into a converter. is there. In these cases, when the briquette is handled, it is apt to be broken and powdered, resulting in a loss due to a decrease in yield. In particular, the oil content causes the crushing strength of the briquette to be reduced, so that the oil content incineration process is required, and eventually the same environmental problems as in the case of (2) above occur.

(4) The oil-containing sludge was dehydrated to a water content of 20 to 40% by weight, cultivated and dried, and then a cement binder was added to the mixture to adjust the humidity, and granulate to produce non-dried cured pellets. , Method for use as steelmaking pellets (Japanese Patent Publication No. 57-4)
No. 3622), the equipment is relatively simple, but the equipment and operating costs are still not cheap and problems remain.

FIG. 2 shows a conventional oil-impregnated sludge treatment process in which oil-impregnated sludge having a high oil content is naturally dried, and sinter or pellets are further produced by a sinter facility or a pellet facility and used as an iron source for a blast furnace. It is a schematic explanatory drawing shown.
As shown in FIG. 2, oil-containing sludge is collected together with water in a sludge collecting tank 1 such as a scale pit or a settling tank, and the oil-containing sludge 2 precipitated in the sludge collecting tank 1 is separated from water and accumulated in the tank. Usually, it is carried out to the ground hopper 4 using the bucket 3 or the like and temporarily stored. Then, the oil-containing sludge 2 cut out from the ground hopper 4 is carried out by the dump truck 5 or carried by the lorry truck 6 in a fluid state, and stored in a reservoir 8 which has been dug out at a predetermined location.
Perform a simple dehydration. At a later date, the shovel car 17 is used to scrape out the oil-containing sludge 2 in the reservoir 8 and convey it to the sun drying field 7 where it is piled up and naturally dried by solar heat for a long time.

After sufficiently air-drying, the oil content in the oil-containing sludge 2 is burnt and removed in the oil content incineration facility, supplied to the sintering facility as a sintering raw material, mixed with other sintering raw materials and sintered. The sinter ore is produced by processing, or it is supplied to a pellet facility, mixed with other raw materials, and reduced to produce pellets. Then, the sinter or pellets are reused as a raw material for the blast furnace. in this case,
Combustion in an oil incinerator to remove oil requires fuel and transportation costs, and equipment cost to install in a cooling fan etc. for cooling after combustion is also required, and operating costs also increase. become. Reusable as sintering raw material or pellet raw material is usually equipped with these manufacturing facilities already, so it is not necessary to newly install most of the equipment except for the necessary hoppers, etc. However, the problem of cost remains as a whole.

[0013]

[Problems to be Solved by the Invention] Since the ring water sludge of a slab of a steel mill or a rolling mill and the ring water sludge of a direct cooling water system of a continuous casting facility have an oil content of 10 to 25% by weight, Even if the iron content was 25 to 40% by weight, it could not be sufficiently recycled as a raw material for iron making, and an inexpensive treatment method therefor was required.

From the above-mentioned circumstances, the reuse of oil-containing iron-containing sludge has a problem contrary to its value as an iron resource, and it is rather cheaper to dispose of it as landfill by disposing of it as industrial waste. There is also. However, even here, there are restrictions such as "oil content of 5% or less" and prohibition of dilution by mixing with other wastes, so sludge with high oil content cannot be discarded and there is no place to go. there were.

In view of the above points, the oil-containing sludge which is difficult to dispose can be diverted by a simple method into a forming sedative for the slag generated in the container during the melting of molten metal. The purpose of the present invention is to provide a slag foaming sedative method.

[0016]

SUMMARY OF THE INVENTION The present invention has been made to meet both the needs of treating oil-containing sludge at low cost and the need of supplying an effective and inexpensive forming sedative. The present invention according to claim 1 for achieving the above, in a slag foaming quenching method at the time of molten metal melting, in which a foam quenching agent is added to slag undergoing foaming in a container for receiving molten metal, wherein moisture is used as the foam quenching agent. A slag foam soothing method during molten metal melting, characterized in that the oil-containing sludge naturally dried to 40% by weight or less is added to the slag during forming.

The present invention according to claim 2 is the method for calming slag foaming during molten metal melting according to claim 1, characterized in that the oil content is added to the oil-containing sludge and then naturally dried. The present invention according to claim 3 is characterized in that the oil-containing sludge is mixed with one or more of coke powder, coal powder, coke powder or dust collecting dust containing coal powder or dust collecting water sludge, and then naturally dried. Claim 1
Alternatively, it is the slag foaming calming method at the time of melting molten metal described in 2.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention focuses on the fact that the oil content of oil-containing sludge, which is a problem when recovering or discarding an iron source, acts as a slag forming sedative,
As a result of pursuing a method that can be recycled at the lowest cost, the shape and strength of the slag foaming sedative are limited as compared to when it is put into a container containing molten metal in a furnace such as a blast furnace or converter. Found that there is little
The present invention has been achieved.

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing a treatment process of the present invention, and shows a treatment process in the case of naturally drying oil-containing sludge having a high oil content and calming the forming of slag generated in a speeded car. As shown in FIG. 1, oil-containing sludge 2 is collected together with water in a sludge collecting tank 1 such as a scale pit or a sedimentation tank. As shown in Table 1, the rolling recycle water sludge generated from thick plate, hot rolled, and shaped steel recycle water has a high iron content and low oil content, whereas the agglomerated lumped recycle water sludge has a low iron content. , Oily. Further, the continuous cooling water sludge of the direct cooling water system of the continuous cast slab has both the iron content and the oil content between them. For use in soothing forming slag, agglomerated ring water sludge with relatively high oil content and continuous cast ring water sludge are more suitable.

[0020]

[Table 1]

The oil-containing sludge 2 having such components is precipitated in the sludge collecting tank 1, and the oil-containing sludge 2 separated from the water 21 is usually carried out to the ground hopper 4 by using the bucket 3 or the like and temporarily stored. Then, the oil-containing sludge 2 cut out from the ground hopper 4 is carried out by a dump truck 5 or carried in a fluid state by a locomotive 6 (see FIG. 2) and stored in a reservoir pond 8 which has been dug out at a predetermined location. Moisture can be removed to some extent by infiltration or evaporation into the ground.

After that, the shovel car 17 is operated to scrape out the oil-containing sludge 2 in the reservoir 8 and move it to the sun drying field 7 to pile it up. The oil-containing sludge 2 piled up is slowly and naturally dried by the solar heat without any trouble, except for performing the tilling work in which the sludge 2 is periodically reversed. If you do this kind of drying work in a large greenhouse,
Since it can be dried more efficiently, and it is not affected by rain or the like, fluctuations in the degree of drying can be reduced. Normally, oil-containing sludge 2 deposited in the sun drying plant 7
The dried oil-impregnated sludge 20 can be obtained by naturally drying in the sun for a long period of about one year while exposing it to rain.

The dryness of the dry oil-containing sludge 20 depends on the water content.
If it is 60 to 70% by weight, the sludge is fluid, and if the water content is too high, there is a risk of causing a steam explosion when added to the molten slag. Since it is hard to be dried, it is necessary to dry the water to 40% by weight or less. In the above description, solar heat was used as a heat source for drying, but in short, the purpose is to evaporate the oil, which is the active ingredient of the forming sedative, and to dry it at a low temperature without burning it, so it is very inexpensive with almost no operating cost. If there is such a hot air source, it is also included in the category of natural drying of the present invention to utilize the hot air source to dry the oil-containing sludge 2 at a low temperature.

The dried oil-impregnated sludge 20 naturally dried in this way is hardened to the extent that it cannot be easily broken by hand, and is in a state in which various lumps of various sizes are mixed, from large lumps to crushed and reduced lands. . However, since the dry oil-impregnated sludge is relatively fragile, it immediately collapses due to the impact at the time of handling, so it is impossible to directly charge the sludge into the blast furnace. Even if it is put into the converter, since it has many fine particles, it is blown up by the ascending airflow from the converter and hardly gets into the slag, so that the forming and calming effect cannot be sufficiently exerted.

Then, the dry oil-containing sludge 20 whose water content is dried to 40% by weight or less in the sun drying field 7 is supplied to the lattice sieve 9 having large meshes by operating the shovel car 18. The dry oil-containing sludge 20 under the sieve from which large lumps have been removed by 9 is put into a hopper 12 provided below the lattice sieve 9.
At this time, the size of the large lump to be removed is determined on the basis of preventing the large lump of 100 mm or 200 mm or more from being suspended in the hopper 12 depending on the device such as the hopper 12. Hopper 12
The dried oil-impregnated sludge 20 put under the sieve is put into a portable hopper 22 and carried into the casting floor above the toped car 11 to prepare for loading.

The hot metal flowing through the hot metal gutter installed in the blast furnace casting bed (not shown) is guided to the tilting gutter 13, and a desiliconizing agent (desiliconizing flux) is poured onto the hot metal in the tilting gutter 13 to remove the siliconizing agent. After desiliconizing by spraying on the surface of the hot metal using
The desiliconized hot metal 10 is received by the tope car 11. At this time, if the viscosity of the slag floating on the desiliconized hot metal 10 received by the pigeon car 11 is high, the slag is generated from the hot metal CO, CO
_Since it expands and bubbles due to bubbles such as ₂ and overflows from the tope car, in order to prevent this, dry oil-impregnated sludge 20 stored in the hopper 22 is cut out by opening the cut gate 19, and the inclined trough 13 inside the tope car 11. It is thrown into the forming slag 15 suspended on the desiliconized hot metal 10 injected into.

When the dry oil-containing sludge 20 is fed from the hopper 22 to the receiving pig iron portion of the speeded car 11, the speeded car 11
Since the ascending airflow from is relatively small and the falling distance is small, there is little loss due to scattering and it is possible to surely make it enter the forming slug 15. This is the point of the present invention in which the dry oil-containing sludge 20 can be recycled as a forming sedative without forming or granulating. Toped car
The CO gas or the like that floats from the desiliconized hot metal 10 in 11 tries to promote the forming by the bubbles that enter the forming slag 15 and float.
In the dry oil-impregnated sludge 20 that has rushed into 15, the gas generated by the evaporation of the oil content contained breaks the air bubbles floating in the slag, so the air bubbles are reduced and the forming can be calmed efficiently.

The gas generated by the evaporation of oil is
Since it is combustible, it heats the forming slag by burning, so that the fluidity is improved by the temperature rise of the slag. For this reason, bubbles such as CO from the slag that has calmed down the forming quickly floats and is diffused into the atmosphere, which facilitates the acceptance of the desiliconized hot metal 10 into the speeded car 11. As a result, not only can the desiliconization treatment by spraying the desiliconizing flux on the hot metal surface using the desiliconizing agent-implanted lance 14 in the inclined trough 13 be performed, but also the toped car
It is possible to increase the amount of pig iron received on 11. Further, it is possible to prevent disadvantages such as the molten slag overflowing on the track on which the speeded car 11 travels, which hinders the travel of the speeded car 11.

With respect to the oil content, even if the oil-containing sludge 2 is used, if the ratio thereof is as small as 2 to 7% by weight, as in the case of the rolling water sludge shown in Table 1, the forming slag 15 is sufficiently sedated. Since the effect cannot be exhibited, it is necessary to add waste oil or the like to replenish the deficient oil content. However, if the oil content becomes too large, it will be difficult to dry, and there is a risk that the oil content will adhere to the equipment for feeding the dry oil-containing sludge 20 and a fire or the like will occur. Also,
Even if the oil content is added to an amount exceeding 15% by weight, the sedative effect of the dry oil-containing sludge 20 on the forming slag is not so improved, so
It is sufficient to replenish it to about 15% by weight.

Further, as means for compensating for the oil shortage of the dry oil-impregnated sludge 20, in addition to waste oil, coke powder and coal powder, particularly dust collection dust of blast furnace exhaust gas as in the prior art disclosed in the above publication, or It is effective to use coke powder and coal powder contained in the collected water sludge as a forming sedative. Therefore, by mixing the collected dust or the collected water sludge with the oil-containing sludge 2 used as the forming sedative, the oil-containing sludge 2 can be diverted as a forming sedative that supplements the oil shortage. If a large amount of coke powder or coal powder is added,
Since the specific gravity becomes lighter and the penetration into the forming slag 15 becomes worse, the upper limit is 30% by weight.

As described above, dry oil-impregnated sludge
The oil content in 20 acts on the forming slag 15 to calm the forming, but the iron content is reduced by reacting with the silicon content and carbon content in the hot metal, and is recovered as the iron source in the hot metal. It can serve as a recycling tool. <Example 1> Agglomerated sewage sludge containing the oil shown in Table 1 was stored in a reservoir pond dug on the ground and left for 2 months, then operated by a shovel car to be dug out and piled up on a sun drying field. Then, it was naturally dried on the sun for 10 months. Once every two or three months on the way, the piles were re-loaded three times so that the inside of the pile was exposed and the natural drying was promoted. A year later, the water content became 15 to 39% by weight, and the dry oil-containing sludge that had become lumpy or sandy was removed using a slit-like lattice sieve to remove large lumps of 200 mm or more, and put into a portable hopper to form a casting floor. Transported.

The desiliconizing agent was sprayed onto the surface of the hot metal in the inclined pouring trough installed in the casting floor using a desiliconizing agent-driving lance, and the desiliconized hot metal was received in the slag of the torpedo car in which the forming was remarkable in the hot metal. The cut gate was opened from the portable hopper and 20 to 40 kg / cycle was thrown in. As a result, the slag forming was subsided, and the slag upper surface level in the toped car was found to drop in 9 to 27 seconds. The decrease in the slag surface in the toped car tended to be faster when the amount of one-time injection was large. <Example 2> About 10% of waste oil (cutting emulsion) in terms of weight ratio of wet sludge was added to the continuous casting ring water sludge containing the oil shown in Table 1 above, and the waste oil (cutting emulsion) was used in a lorry wheel and a reservoir. After mixing and stirring, the dried oil-containing sludge, which was naturally dried in the same manner as in Example 1, was added to the slag forming in the toped car at an amount of 30 kg / time. As in the case of Example 1, the forming of the slag was subsided, and a decrease in the upper surface of the slag was observed in 10 to 30 seconds. As a comparative example, an experiment was conducted on sludge to which waste oil was not added, but it took 15 to 40 seconds for the slag surface to decrease even with the same amount of input, and the slag sedative effect was slower than that of mixing waste oil. <Example 3> The wet sludge shown in Table 2 which was collected by a wet dust collector of blast furnace exhaust gas instead of the waste oil of Example 2 in the oil-containing continuous casting ring water sludge shown in Table 1 and settled on thickener Was mixed about 50%, and the dried oil-containing sludge which was naturally dried in the same manner was added to the slag forming in the speeded car at an amount of 30 kg / time.
Deterioration time of slag upper surface by forming calming is 8 ~
It was 22 seconds.

[0033]

[Table 2]

In the above-mentioned embodiment, the case where the slag is calmed down by adding the dry oil-containing sludge as a calming agent to the forming slag floating on the desiliconized hot metal in the tope car has been described. However, the present invention is not limited to this. However, the dried oil-impregnated sludge can be widely applied to calming slag formed on molten metal such as hot metal and molten steel contained in a container such as a toped car, a hot metal ladle, and a molten steel ladle.

[0035]

As described above, according to the present invention, the oil-containing sludge which is difficult to dispose can be used as a slag forming calming agent by simply and naturally drying the oil-containing sludge and containing the molten metal. The dry oil-impregnated sludge can be plunged into the slag forming in the ladle with good yield without special molding or granulation. Since the dry oil-containing sludge has a high effect as a soothing agent for forming slag and also has an advantage as a recoverable metal source, its economic effect is great. In addition, the value of the effective use of oil-containing sludge, which is a waste, in preventing environmental damage cannot be overlooked.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a treatment process of an oil-containing sludge according to the present invention.

FIG. 2 is a schematic explanatory view showing a conventional oil-containing sludge treatment process.

[Explanation of symbols]

 1 Sludge collecting tank 2 Oil-containing sludge 3 Bucket 4 Ground hopper 5 Dump truck 6 Lorry vehicle 7 Sun-drying field 8 Storage pond 9 Lattice sieve 10 Desiliconized hot metal 11 Topeed car 12 Hopper 13 Slanting gutter 14 Desiliconizer driving lance 15 Forming slag 16 Dust hood 17 Excavator car 18 Excavator car 19 Cut gate 20 Oil-impregnated sludge 21 Water 22 Portable hopper

Claims (3)

[Claims] 1. A slag foaming quenching method for melting molten metal, wherein a foam quenching agent is added to slag being formed in a container for receiving molten metal, wherein the foaming quenching agent naturally has a water content of 40% by weight or less. A method for calming slag foaming during molten metal melting, which comprises adding dried oil-containing sludge to slag during forming. 2. The method for calming slag foaming during melting of molten metal according to claim 1, wherein the oil content is added to the oil-containing sludge and then naturally dried. 3. Oil-containing sludge, coke powder, coal powder,
The slag foaming soothing method at the time of molten metal melting according to claim 1 or 2, wherein at least one of dust collecting dust or dust collecting water sludge containing coke powder or coal powder is mixed and then naturally dried. .