DE2623264A1 - LANCE AND METHOD FOR INTRODUCING A MIXTURE OF REACTIVE PARTICULATE MATERIAL AND A CARRIER GAS INTO MELTED IRON TO BE DESULFURIZED - Google Patents

Description

PAT ENTANWÄLTE MENGES & PRAHL 2623264

Erhardtstrasse 12, D-8000 Munich 5

Patent attorneys Menges & Prahl, Erhardtstr. 12, D-8000 Munich 5 Dipl.-Ing. Rolf Menges

Dipl.-Chem. Dr. Horst Prahl

Telephone (089) 26 3847 Telex 529581 BIPATd Telegram BIPAT Munich

Your reference / Your ref.

Our mark / Ourref. I 114

Date May 24, 1976

Jones & Laughlin Steel Corporation Pittsburgh, PA 15230, V.St.A.

Lance and method for introducing a mixture of reactive Particulate matter and a carrier gas in molten iron to be desulfurized

The invention relates to a lance which can be used for the desulfurization of molten ferrous materials such as steel and cast iron. The lance according to the invention is designed so that it both the high withstanding temperatures of about 1430 ° C to 1595 ⁰ C, which normally occur in the molten iron bath, as is also used as a passage for the introduction of various reactive desulphurising at locations below the bath surface . A structurally rigid lance that is thermal shock resistant must be able to withstand the harsh environment of molten iron baths. In addition, the lance must be sufficiently insulated to prevent temperatures from being reached that could

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are sufficiently high to cause the desulphurising agent produced to melt or react with the carrier gas.

The prior art has generally been concerned with finding solutions to certain aspects of problems which are similar to that achieved by the invention. Example sse'ise a fluid-cooled lance is described in US Pat. No. 2,805,147, which can be used for introducing fine-grained solid additives, such as magnesium, together with a Carrier gas, such as nitrogen, beneath the surface of metallic melts. According to the In accordance with the invention, however, a rigid, insulated lance is used for desulfurization instead of a fluid-cooled lance, thereby minimizing operational complexity and related design and manufacturing problems. U.S. Patent 3,430 deals with a compound injection lance that is intended for use in oxygen steel manufacturing processes. Aluminum foil layers are used in such lances used and they are described as self-consuming.

A typical desulfurization process for hot metals involves the introduction of straight, refractory-coated steel pipes, which introduce powdered desulfurizing agents at an angle of 20 ° to 40 ° to the horizontal into pig iron mixers that contain the molten pig iron before it is transported on and refined into steel, for example by known processes such as the Siemens-Martin or basic oxygen blowing process. This known desulfurization method is advantageous in that the desulfurizing agent can be introduced near one of the ends of the pig iron mixer, which results in good mixing of the desulfurizing agent with the pig iron due to the circulation of the molten pig iron created in the mixer. The lances are, due to. Considerations regarding the exchange ^ structured as follows ₉

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that they are light in weight.

On the other hand, the typical known system has several disadvantages. First, the pig iron mixer has to be driven by a locomotive precisely positioned to ensure that the lance, given the angular position, is exactly in the mouth or upper opening of the mixer can be introduced. Second, the mouth of the mixer must be free of muzzle rings and slag build-up to prevent breaking or bending to prevent the lance. The slag build-up below the mixer ceiling or on its bottom helps that the lance breaks or that its tip is blocked. Finally, extensive injection treatments, such as those required, lead over a long period of time lowering the sulfur content from about 0.100% to 0.010% causes overheating of the pipe and, consequently, softening and bending due to the buoyancy of the denser pig iron and the agitation of the mixing process. The times involved in the above-mentioned desulfurization are usually in the range of 15 minutes to ·. 45 minutes.

It can therefore be seen that the typical method and lance system described above is not altogether satisfactory in the case of lengthy desulfurization treatments. That is true especially in cases in which there is strong slag formation or in which the desulphurizing agent has a relatively low melting point and reacts with the carrier gas. It is clear that the latter case is a more complex one Lance system is required in order for a satisfactory service life to be achieved without it becoming clogged or the system is blocked.

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The system according to the invention has been designed mainly for solving problems, the known systems are peculiar. It comprises a total of a rigid, open-ended, elongated conveying pipe, which of a layer of insulating material is surrounded, which in turn is surrounded by a second tube, which is with a Layer of refractory material is covered. The insulation quality and construction strength of the lance is so large that the lance can be used for prolonged and repeated use in desulfurization processes and one Has sufficient insulating property so that reactive particulate material, such as magnesium or its Alloys, with a carrier gas, such as nitrogen, can be introduced without affecting the particulate material melts or reacts with the nitrogen. In use, the lance can be inserted vertically into a mixer thereby avoiding many of the problems encountered in the prior art.

The invention thus provides a lance which has sufficient structural strength to withstand a time-extended lance Enduring use in the desulfurization of molten ferrous metals.

The invention also creates a lance system, its insulating capacity is so great that prolonged use in the introduction of magnesium-containing particulate matter and Nitrogen in iron melts does not melt the particulate material or react with the nitrogen thereby avoiding clogging or blocking of the system.

Further features and advantages of the invention emerge from the following description of an exemplary embodiment of FIG Invention illustrated in the drawings. Show it:

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Fig. 1 is a sectional view of the lance which the

shows various layers surrounding the conveyor pipe that contribute to the structural Lead to rigidity and strength as well as to the desired insulating properties, and

Fig. 2 illustrates a method of application of the

Lance according to the invention in connection with a pig iron mixer.

The lance according to the invention can be referred to as a composite lance will. From FIG. 1 it can be seen that the lance has different layers which surround an inner tube 11. This tube is a rigid, open at the end, elongated conveyor tube, the end 16 of which for connection to a conventional Feed line (not shown) for introducing a mixture of particulate material and a carrier gas into the tube 16 is provided. The pipe end 18 is used for introduction of the conveyed mixture beneath the surface of molten material. It is clear that different configurations of openings and / or nozzle inserts for introducing the mixture under the surface of various Molten ferrous materials can be used. However, the circular configuration shown in FIG. 1 is sufficient for the purposes of the invention. A common steel pipe is suitable for the pipe 11. But others could too heat-resistant materials are used.

A layer of insulating material 12 is around the conveyor pipe 11 arranged around and in direct contact with the same. The insulating material layer should have a sufficient thickness to prevent the reactive particulate material from melting and reacting with the carrier gas.

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Different types and thicknesses of insulation are suitable for these purposes and depending on the type of mixture to be introduced addicted. For the introduction of magnesium-containing particulate materials with nitrogen as the carrier gas is a 6 mm to 12.5 mm thick layer of kao wool or Asbestos in tissue form has been used with success.

A second rigid tube 13 is placed around and in direct contact with the insulating material layer 12. The tube 13 serves the purpose of providing the structural rigidity required for the inventive Use is required. Without the presence of the second pipe, at the temperatures that occur during the Initiation process occur, resulting in an impermissible amount of bending and / or deflection. The pipe 13 can be made from the same materials that have been specified for the conveyor tube 11 above. The pipe 13 can also be designed for connection to certain parts associated with material introduction devices are, as in the case of the conveyor pipe 11. This aspect is shown at the pipe end 17. The pipe 13 is in turn with a layer of refractory material 14 provided, of a composition and of sufficient thickness to withstand the erosion caused by the molten Iron is caused during the process. The refractory layer 14 also serves to make the lance so To insulate far that the particulate material does not melt during its passage through the conveyor tube 11 or with reacts to the carrier gas. It has been found that annular refractory sleeves, such as those used for steel ladle locking rods are used, and which are so large that they fit on the pipe 13, are arranged around the pipe 13 around can. Such a refractory material is, for example, a 12.5 mm thick silicon-containing refractory material. Wedge-shaped sections are used in the area where the lance is bent. To prevent leakage

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between the sleeves can be a thin layer of air-drying Slurry such as that available from Miller Refractories Co., 8901 Woodland Avenue, Cleveland, Ohio 44104, manufactured so-called Miller's Stopper Rod Cement. Of course you can instead of the refractory type and ring shape described above, various other types and shapes or dried slurries can be used provided that they perform the required function.

It is preferred to create a bend near the inlet end of the lance. The optimal distance will be 60 viewed up to 90 cm from its end. Such a bend should typically coincide with the longitudinal axis of the tube 11 Make an angle of 30 ° to 45 ° so that the lance is lowered vertically into the iron bath and then the mixture under a Downward angle can be introduced into the bath. Such introduction serves to promote the mixing of the Particulate matter and the bath, as this promotes circulation. A typical bend configuration is on the point 15 shown in FIG.

As FIG. 1 shows at point 18, is the tip of the conveying tube 11 essentially with the three cover layers of the lance flush. This arrangement is preferred because of particulate build-up and / or backflow This prevents hot molten material from entering the lance will. Thus, there is a longer lance life due to the reduced opportunity for lance clogging. This aspect is for the introduction of reactive particulate material with a low melting temperature, such as magnesium and magnesium alloys, are particularly important.

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It has been found that lances according to the invention can typically be used for five to eight desulfurization treatments, each of which has a duration of about 15 to 25 minutes. In contrast, just refractory coated steel pipes have a useful life of about two desulfurization treatments when used to introduce magnesium-free desulfurizers such as calcium carbide, and less than one treatment when used for magnesium-containing powders. Typical particulate materials containing magnesium include: pure magnesium powder, magnesium-aluminum alloys, and magnesium-calcium alloys. Typical size ranges suitable for practicing the invention are from about 0.30 to 0.85 mm. The introduction of such powders tends to clog the lance during the early stages of treatment and thereby quickly become inoperable. Magnesium and its alloys melt at relatively low temperatures of, for example, about 425 ^° C. to 593 ° C. and then react quickly with the nitrogen serving as the carrier gas. Therefore, when magnesium-containing powders are introduced into molten iron, the lance should be sufficiently insulated to ensure that the temperature rise in the conveyor tube 11 does not exceed about 425 ° C. during the process. The reaction leads to the build-up of reaction products on the walls or near the tip of the conveying pipe 11.

Instead of inserting the lance at an angle to the horizontal, As is done in the prior art described above, the lance according to the invention is vertically into the Bath lowered. This method is shown in Fig. 2, which shows the lance 21 in connection with a pig iron mixer 22 shows. The lance shown with dashed lines 23 shows the position of the lance 21 before it is inserted into the Mixer 22. Through a bend in the lower part of the lance,

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As shown in Fig. 1, the supply and the effective utilization of the mixture of the carrier gas and the reactive particulate material facilitated. If necessary, the lance can be designed to be pivotable by 5 to 15 about its axis to ensure that the lance is inserted at the top under the ceiling of the pig iron mixer 22. This makes it easier to insert the lance into the mixer 22 and also improves the effectiveness of the desulfurization process promoted.

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Claims (6)

Patent claims: π. Lance for introducing a mixture of reactive Particulate matter and a carrier gas beneath the surface of molten iron material to be desulfurized, with a rigid, open ended, elongated conveying tube having a first end which is used for connection is provided with a feed device for introducing the mixture into the conveying pipe, and a second End that serves to keep the mixture below the surface of the molten liquid after it has passed the conveying pipe To initiate ferrous material, characterized by: a) a layer of insulating material disposed around and in direct contact with the conveyor pipe; and is of sufficient thickness to prevent the particulate material from melting and reacting with the carrier gas, b) a second rigid tube placed around and in direct contact with the layer of insulating material is and c) a layer of refractory material placed around and in direct contact with the second tube and is of such a composition that it is resistant to erosion when mixed with molten iron material is brought into contact and is of sufficient thickness to allow the particulate material to melt and react to prevent with the carrier gas. 2. Lance according to claim 1, characterized in that it is bent near the second end at an angle of about 30 to about 45 from its longitudinal axis. 3. Lance according to claim 1 or 2, characterized in that the second end of the conveyor tube substantially with the 609853/0667 Insulating material, the second pipe and the refractory material is flush. 4. Method of introducing a mixture of reactive Particulate matter and a carrier gas beneath the surface of molten iron material to be desulfurized, characterized in that the lance of claim 1 is used to sub-surface the mixture to introduce the molten ferrous material, without the particulate material melting and without any reaction between the particulate material and the carrier gas comes. · 5. The method according to claim 4, characterized in that the particulate material comprises a part which consists of the Group selected that consists of magnesium, magnesium-containing alloys and magnesium-containing compounds and that the carrier gas contains nitrogen. 6. The method according to claim 5, characterized in that a temperature of no more than about 425 ° C is established in the delivery tube during use of the lance. 609853/0667