AT509894A1 - METHOD AND DEVICE FOR PRODUCING OVERHEATED SATURATING STEAM IN A CONTINUOUS CASTING MACHINE - Google Patents

Description

uii 20-0 17:15 201010110

Siemens CIC P

No. 3 * 43 p. 5 * «« · M · * • · * * * · 1

Description / Description

Method and device for producing superheated saturated steam in a continuous casting machine 5

The present invention relates to a method and apparatus for producing superheated saturated steam in a continuous casting machine, and to the use of the apparatus in a continuous casting plant to produce a steel strand. 10

Specifically, the invention relates to a method for producing superheated saturated steam in a continuous casting machine, comprising the following method steps: introducing a metallic melt into a mold; 15 - cooling the melt in the mold to form a solid strand shell, - - extracting an at least partially solidified strand of the mold; Guiding, supporting and cooling the drawn strand in a strand support device.

In the continuous casting of a metallic melt into a strand, for example, liquid steel is poured into a downwardly open mold, the so-called mold, wherein the molten metal is cooled mainly via the mold walls, so that a stable strand shell is formed in the mold. The strand, which is at least partially solidified, is subsequently drawn out of the mold and guided in a strand support device arranged downstream of the mold, supported and further cooled. Often, the cooling of the

Molten metal in the mold also referred to as primary cooling and the cooling of the drawn strand in the strand support means as secondary cooling. It is known to form the mold walls of copper plates, wherein the mold walls on the back, i. on the

Molten metal side facing away, to be cooled by cooling water. Typically, the flow rate of the cooling water through the mold is selected so that the cooling water is $ CIO 3

No. 3443 p. 6, · # · · · 201010110

2 to itiax. 10 ÖC is heated. Although the amount of heat dissipated by the cooling water is high with up to 2 MW / m2 of mold surface, this amount of heat can not be supplied to heat recovery due to the small temperature swing. Due to the high flow rates of the cooling water through the mold, there are also high pressure losses, so that high overall performance is required for the circulating pumps of the primary cooling circuit. From JP 1143743 A2, it is known to insert a plurality of heat pipes into the jacket of a Integrate mold, so that the overall thermal conductivity of the mold is increased. Although heat pipes may be advantageous, a direct use of the vaporized inside the heat pipes 15 cooling medium is not possible.

From CN 2379234 Y it is known to supply the heat of vaporization of a casting process of heat recovery; However, from the disclosure there are no starting points as to how the proposed device would be applicable to iron or steel materials in a conventional continuous casting machine (for example, a bow or vertical machine). Furthermore, the generated steam has only a low energy content. 25

The object of the invention is to specify a method and a device for generating superheated saturated steam in a continuous casting machine, in which a saturated steam produced has a high energy content, so that this 30 can be directly fed to a heat recovery with a steam turbine.

This object is achieved by a method of the type mentioned, in which by cooling the melt, a cooling medium in at least one evaporation chamber of the mold is vaporized by means of nucleate boiling to saturated steam and the saturated steam is superheated to a superheated saturated steam. 01/06 2010 Tue 17:18 [SE / EM NR 7303] @ 006

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Siemens CIC F r. 3443 p. 7

By evaporating the cooling medium in at least one evaporation space (for example, the space between a copper plate and the water box) of the mold by means of nucleate boiling to saturated steam, a very good heat transfer, i.e., heat, is achieved. ensures a high heat transfer coefficient, between the mold and the cooling medium, so that in particular a top heating of the copper plates of the mold is reliably prevented. Under nucleate boiling, see, for example, Fig. 9.2 in John H. Lienhard, or the curve region between points A and C (partial nucleate boiling and fully developed nucleates boiling) in the "typical boiling curve" at http://encyclopedia2.thefreedictionary.com/boiling) is understood to mean boiling in a range between natural convection and the point of maximum heat flux density. Since the evaporation of the cooling medium in the evaporation space directly, i. can be done without a DC link, the process is very simple and inexpensive to carry out.

The subsequent overheating of the saturated steam directly higher and - at least for conventional Wärmeruckgewinnungsprozesse - better usable 25 temperature level of the cooling medium is reached, so that the superheated saturated steam can be fed directly to a steam turbine 2u. In addition, efficiency is increased by the top heat of Carnot's heat (see, e.g., http: //en.wikipedia.orq/wiki/Carnot-Wirkunqsqrad). 30

It is advantageous that overheating is overheated by passing the saturated steam through cooling of the strand, wherein the saturated steam is guided in at least one line along at least one surface of the strand. The 35 saturated steam z, B, is passed through partially or fully solidified steel slabs. 01/06 2010 Tue 17:18 [SE / EM NR 7303] @ 007

Sienens C IC? 1st J. r! 2010 17:19 201010110

According to a simple, advantageous embodiment, the superheated saturated steam is expanded in a steam turbine. Steam turbines are available for different capacities and have a high efficiency. 5

According to an advantageous embodiment, the method for producing saturated steam is designed as a cyclic process, in particular that the cooling medium after the relaxation, and optionally a subsequent condensation, again the mold 10 is supplied.

According to a simple embodiment, water is used as the cooling medium, the saturated steam having a temperature of 200 to 400 ° C. before the expansion. 15

According to an alternative embodiment, an organic cooling medium, e.g. an alcohol or thermal oil, the saturated steam having a temperature of 180 to 400 ° C prior to relaxation. Since organic cooling media can be expanded in 20 available steam turbines, it is generally not necessary to provide first and second circuits connected to the first circuit via at least one heat exchanger. In this embodiment, however, it is in principle possible to divide the cooling in two separate circuits, wherein the first circuit is operated with the organic cooling medium and at least the mold and the superheater comprises, and the second circuit is operated with water and at least the steam turbine and comprises a capacitor. In this case 30 both circuits would be e.g. coupled via at least one heat exchanger connecting the first to the second circuit. Of course, in the two-loop embodiment, it is also possible to use inorganic cooling media, e.g. To set a defined vapor pressure in the evaporation space of the mold, it is advantageous that the pressure of the saturated steam in the evaporation space of the mold by means of 01/06 2010 DI 17:18 [SE / EM NR 7303] @ 008 35

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5 of a vapor pressure adjusting device is set to a predetermined pressure. This measure has a favorable effect especially when starting the continuous casting. The most direct implementation of the method according to the invention is possible if the continuous casting machine - a cooled mold for casting a metallic melt to an at least partially solidified strand, wherein the mold is formed with at least one evaporation space for the production of saturated steam; and - one of the mold subordinate strand support means for supporting, guiding and further cooling of the strand; , wherein - the mold with at least one steam turbine to 15 overheating of the saturated steam is formed connectable.

Preferably, the superheater is designed as a secondary cooler or a secondary cooling section of the continuous casting machine. As a result, the quantity of heat dissipated by means of the secondary cooling of the partially or thoroughly solidified strand is also absorbed by the saturated steam.

It is advantageous that the superheater is formed with a steam turbine for relaxing the saturated steam connectable 25. Of course it is also possible to arrange several steam turbines in parallel and / or in series. A parallel arrangement is advantageous for realizing higher power with several smaller steam turbines; a serial arrangement is advantageous to better exploit the pressure level of the saturated steam, for example by a

High-pressure and a subsequent low-pressure steam turbine. Of course, it is also possible, for example, to arrange several high-pressure steam turbines in parallel and then, i. in serial arrangement to arrange one or more low-pressure steam turbines. 01/06 20 10 01 17:18 [SE / EM NR 7303] @ 003

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Advantageously, at least one line in the superheater is formed meander-shaped for uniform cooling of the strand. According to one embodiment, the steam turbine with at least one condenser and the condenser are connectable via at least one feed pump to the mold. Advantageously, a condenser is arranged in a cooling section, preferably in a cooling section in the outlet region of the continuous casting plant or in a cooling section in the outlet region of a rolling mill downstream of the continuous casting machine. 15

In order to achieve a high thermal conductivity of the mold at the same time high thermal shock resistance of the mold, it is advantageous that the mold at least in the region of the meniscus in a direction transverse to the casting 20 a ceramic or ceramic-metallic

Layer, a sheet of copper or a copper alloy, a ribbed plate for evaporating the cooling medium and a holding plate. It is advantageous to use the device according to the invention in a continuous casting plant for producing a strand of steel.

Further advantages and features of the present invention will become apparent from the following description of non-limiting embodiments, reference being made to the following figures, which show:

Fig. 1 is a schematic representation of a continuous casting machine 35 with heat recovery

2 shows a schematic diagram of the thermodynamic state variables of the continuous casting machine with heat recovery 01 / 0E 2010 01 17:18 [SE / EM NR 7303] ®010 f jn; 2010 17:19

3ienes CIC F Ν '. 3443 s. 11 201010110 ·· ··· ·· ··· * 7

3 shows a schematic representation of a superheater which is integrated into the secondary cooling of the continuous casting machine FIG. 4 shows a schematic representation of a condenser which is integrated into a cooling section FIG. 5 shows a schematic representation of the construction of a mold

1 shows a continuous casting machine for producing steel slabs, which generates saturated saturated steam by means of the waste heat arising from the continuous casting process 10. In this case, a molten steel is introduced by means of a pan, not shown, via a distributor in a mold 2, in which the melt is cooled by means of the primary cooling 3, wherein a solid strand shell is formed. The partially solidified strand 12 thus forming is drawn out of the mold 2 and guided in a strand support device 5 downstream of the mold 2, supported and further cooled by means of the secondary cooling. The strand support device 5 has a plurality of strand guide 20 not shown in detail, each having a plurality of both sides of the strand 12 arranged strand guide rollers 5a. By means of the mold 2, the initially liquid cooling medium of about 35 ° C (point II) is heated to about 200 ° C (point III) and then evaporated in several evaporation chambers of the mold 25 by means of nucleate boiling to saturated steam (point IV). A large part of the molten steel or the partially solidified strand 12 extracted heat is absorbed by the cooling medium and thus increases the entropy of the cooling medium (see Fig, 2). The saturated steam is supplied via a steam line to a superheater 430, in which the saturated steam is passed over at least one meandering line over the approximately 900 ° C hot slab and in turn absorbs energy; In this case, the saturated steam of about 200 ° C (point IV) is overheated to about 330 ° C (point V). Subsequently, the superheated 35 saturated steam is fed by means of a steam line to a steam turbine 7, in which the steam from point V to point VI relaxes and the energy released by means of a shaft between the steam turbine and a generator 8 in 01/06 2010 DI 17: IS [SE / EM NR 7303] @ 011 1. Jun 2C1G Π: 19

S i emens CIC P

No. 3443 p. 12 201010110 8 electrical energy is converted. Subsequently, the cooling medium is first fed to a first condenser 9 and then to a second condenser 9a in which the entropy of the cooling medium is further reduced. The first capacitor 5 9 is as part of the cooling section 10 in the outlet region of

Continuous casting machine arranged in the solidified strand 12 is cooled by means not shown nozzles to near room temperature (point I). At least one circulating pump 11 increases the pressure of the cooling medium, so that this again the steam generator 1, i. the primary cooling 3 of the mold 2, is supplied.

The thermodynamic state variables assumed in the process according to FIG. 1 are again summarized in FIG. 2 in an entropy-temperature diagram.

In Fig, 3, a superheater 4 is shown schematically. In this case, the saturated steam is guided in at least one meandering line 13 at a small distance over the surface of the partially or 20 durcherstarrten strand 12, wherein the strand is cooled further and thereby a large part of the heat dissipated thereby used for overheating of the saturated steam. Preferably, the meandering line 13 is counter-flowed against the casting direction 15, so that while the saturated steam 25 initially absorbs energy from a colder strand and later energy from a warmer strand.

4, a capacitor is shown schematically. At the top of the strand 12, the strand is cooled by several 30 spray nozzles 14, wherein the resulting cooling water is used for condensation of the cooling medium within a meandering line 13. In contrast to the superheater shown in FIG. 3, the condenser 9 is flowed in the casting direction 15, so that the cooling medium is initially cooled by a warmer cooling water and later by a colder cooling water. If the temperature of the cooling medium can not be reduced sufficiently by this process, it is of course 01/06 2010 DI 17:18 [SE / EM HR 7303] @ 012. Jun. 20IG 17:19 201010110

Siemens CIC P

No. 3 ^ 3 p., 3

possible, instead of the one in fig. 4, condenser 9a according to Fig. 1, embodiments of capacitors, for example, Dubbel, Taschenbuch für die Maschinenbau, 5 17th edition, chapter K22 "Components of the thermal

Apparatus construction - 4 condensation and recooling ").

In FIG. 5, the construction of a mold 2 in a direction transverse to the casting direction 15 is shown schematically, the representation of the dip tube having been omitted for reasons of clarity. Between the steel 16, which forms a partially solidified strand in the mold, and the mold 2, there is a layer on casting powder 17 to reduce the friction between the strand and the mold. Since the mold 2 becomes substantially hotter than a prior art mold due to evaporative cooling, the copper plate 19 of the mold has a highly abrasion-resistant, wear-resistant layer of a ceramic 18 or composites of ceramic materials in a metallic matrix (a so-called cermet

Material, see e.g. http://de.wikipedia.org/wiki/Cermet).

Subsequent to the copper plate of Cu or a Cu alloy is a ribbed plate 20 which has a plurality of extending in the casting direction and / or in a direction transverse to the casting direction 25 ribs 21. By means of this construction, the effective surface of the mold is increased, so that particularly high amounts of heat can be dissipated by the mold (for example 3 MW / m2, this value being based on the wetted by the steel mold surface 30), without it a movie boiling comes.

Between the ribs 21 of the ribbed plate 20, there is the evaporation space 23 of the mold, in which the cooling medium water is evaporated to saturated steam. Following the ribbed plate 21 is a holding plate 22, the 35 by means of several designed as screws

Fasteners is connected to the ribbed plate. 01/06 2010 Tue 17:18 [SE / EM KR 7303] @ 013 1. L'i 201C 17:19

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10

List of Reference Signs / Reference Signs List 1 Steam generator 2 Mold 3 Primary cooling 4 Superheater 5 Strand support 5a Strand guide roll 6 Secondary cooling 7 Steam turbine 8 Generator 9, 9a Condenser 10 Cooling section 11 Pump 12 Strand 13 Mörane shaped line 14 Spray nozzles 15 Casting 16 Steel 17 Casting powder 18 Ceramics 19 Copper plate 20 Ribbed plate 21 Rib 22 Retaining plate 23 Evaporation space I-II Pressure increase 2I-III Heating to evaporation temperature III-IV Evaporation iv-v Overheating v-vx Relaxation VI-I Condensation 01 / 0B 2010 DI 17:18 [SE / EM HR 7303 ] @ 014

Claims (16)

June 2010 17: 1 9 Siene na C i CF No. 3443 p. 15 · · 201010110 11 Claims 1. A process for producing superheated saturated steam in a continuous casting machine, comprising the following 5 process steps: - introducing a metallic melt into a Mold (2); - cooling the melt in the mold (2) to form a solid strand shell; 2. The method according to claim 1, characterized in that the saturated steam is overheated by cooling the strand (12), wherein the saturated steam is guided in at least one line along at least one surface of the strand. 25 3. The method according to any one of the preceding claims, characterized in that the superheated saturated steam in a steam turbine (7) is relaxed. 4. The method according to any one of the preceding claims, characterized in that the method for generating superheated saturated steam is designed as a cyclic process, in particular that the cooling medium after the relaxation, and optionally a subsequent condensation, again the mold 35 (2) is supplied. 5. The method according to any one of claims 3 to 4, characterized in that water is used as the cooling medium and 01/06 2010 DI 17:18 [SE / EM NR 7303] @ 015. -June 2010 '7:19 Siemens CIC P No 3443 p. 16 201010110 12 the saturated steam has a temperature of 200 to 400 ° C prior to expansion. 6. The method according to any one of claims 3 to 4, characterized 5 characterized in that an organic cooling medium, in particular an alcohol or a thermal oil, is used and the saturated steam at a temperature of 180 to 400 ° C prior to relaxation. 7. The method according to any one of the preceding claims, characterized in that the pressure of the saturated steam in the evaporation chamber of the mold is adjusted by means of a vapor pressure adjusting device to a predetermined pressure. 15 8. A device for generating saturated steam in a continuous casting machine, comprising - a cooled mold (2) for casting a metallic melt to an at least partially solidified strand (20), wherein the mold (2) is formed with at least one evaporation space for generating saturated steam ; - One of the mold (2) downstream strand support means (5) for supporting, guiding and further cooling of the strand (12); Characterized in that the mold (2) is designed to be connectable to at least one superheater for overheating the saturated steam. 9. The device according to claim 8, characterized in that 30 of the superheater (4) is designed as a secondary cooler (6) or a secondary cooling section (6) of the continuous casting machine, 10. Device according to one of claims 8 to 9, characterized 35 in that the superheater (4) with a steam turbine (7) for relaxing the saturated steam is formed connectable. 01/06 2010 Tue 17:18 [SE / EM NR 7303] @ 016 -uni 2010 17:20 i m e π = \ r. 34-43 s. 17 201010110 10 - Extracting an at least partially solidified strand (12) from the mold (2); - guiding, supporting and cooling the extended strand (12) in a strand support device (5); characterized in that: - cooling the melt by evaporating a cooling medium in at least one evaporation space of the mold (2) to saturated steam by means of nucleate boiling; and "that the saturated steam is overheated to a superheated saturated steam. 20 11. Device according to one of claims 8 to 10, characterized in that at least one line in the superheater (4) meandering for uniform cooling of the strand (12) is formed. 5 12. The device according to one of claims 10 to 11, characterized in that the steam turbine (7) with at least one capacitor (9) and the capacitor (9) via at least one feed pump to the mold (2) are formed connectable. 10 13. The apparatus according to claim 12, characterized in that a capacitor (9) is arranged in a cooling section (10), 14. Device according to one of claims 8 to 13, characterized in that the mold (2) at least in the region of the meniscus in a direction transverse to the casting direction (15) has a ceramic or ceramic-metallic layer, a plate made of copper or a copper alloy, a ribbed plate 20 for evaporating the cooling medium and a holding plate. 15. Device according to one of claims 8 to 14, characterized in that an evaporation space in the interior of the mold with an optionally adjustable, 25 pressure limiting device is connected, so that the pressure of the saturated steam is adjustable. 16. Use of the device according to one of claims 8 to 14 in a continuous casting plant for producing a strand of 30 steel. 0 1/06 2010 Tue 17:16 [SE / EM HR 7303] @ 017