EP3238857B1 - Two material secondary cooling for a continuous casting plant - Google Patents

Description

Technical area

The invention relates to a device and a method for multi-material secondary cooling in a continuous casting plant, wherein a multi-substance coolant, preferably an air / water mixture, is applied in a secondary cooling zone on surfaces of the cast strand.

Background of the invention

In the continuous casting of slabs, it is known to provide secondary cooling of the cast product, i. a cooling which takes place after the exit of the slab from the mold to perform. In this case, a cooling medium, which is for example water or a mixture of air and water, is applied or sprayed onto the metal surfaces of the slab to be cooled. The slab or cast strand is deprived of heat by evaporation and / or heating of the cooling medium. For the casting of different steel grades in a wide range of different casting speeds, a large adjustment range is required concerning the cooling intensity, which is determined by various parameters, including the Wasserbeaufschlagungsdichte.

The FIG. 1 shows a schematic of a conventional water-secondary cooling for a continuous casting plant. Here, water from a reservoir 10 by means of a pump 20, which may be a simple or frequency-controlled water pump, placed in a water distribution network 30. For the regulation of the water volume flow control valves 31, for example piston valves, are used. The control valves 31 may be equipped with a valve control and / or a volumetric flow meter, together with the reference numeral 32, to regulate and measure the volume flow via a piping to the nozzle 33. The continuous casting plant may have one or more so-called overflow control valves 34, which have an excess amount of water between the water pump 20 and branch off the control valves 31 and lead into a sintering trough 35. The device of FIG. 1 is schematically divided into three sections, wherein the reference numeral A denotes a fixed part of the installation, a media room or distribution room, the reference numeral C denotes a continuous casting segment in the vicinity of the cast strand in which the nozzles 33 for dispensing coolant, and the reference symbol B denotes a section, in which a piping as part of the water distribution network 30, the water from the distribution chamber A to the continuous casting C feeds.

A conventional water nozzle 33 of simple construction has a fixed orifice for discharging the water. This leads to an invariant pressure / volume flow characteristic, in which each pressure, for example in the pressure range of 0.5 to 12 bar, exactly one water flow point is assigned. The desired water volume flow is adjusted with the aforementioned control valve 31 (also referred to as a volume flow control valve) in the distributor room. In the mentioned pressure range of 0.5 to 12 bar, the single-fluid nozzles 33 have a relatively small adjustment range of approximately 1: 3.2 with respect to water flow. The water-secondary cooling system is not very flexible in this sense. Furthermore, the regulation or change of the volume flow can lead to an energy loss. For if the control valves 31 are designed, for example, as piston valves, a large amount of energy of the water flow at the ring diffuser of the piston valve is converted into friction, in particular at low water consumption. Conventional flat jet or full cone spray pattern nozzles are subdivided along standardized volume flow and jet angle graduations and assigned to the secondary carpet zone nozzle carpet according to a system design tradeoff. Another disadvantage of the system described concerns the maintenance required to remove residues on the nozzles, especially lime deposits. Such deposits occur especially at low water flow rates. The small cross-sections of the nozzles set quickly.

A further development of the water cooling described above is the secondary cooling as two-fluid cooling by means of an air / water mixture perform. In this case, water is premixed in a mixing chamber with air, and the mixture is fed to one or more nozzles and output as atomized binary mixture. Such a two-fluid cooling is for example in the DE 100 15 832 A1 described.

The FIG. 2 shows a schematic of a conventional dual-fluid secondary cooling for a continuous casting plant. Here are the same, similar or equivalent elements relative to FIG. 1 provided with identical reference numerals, and a repetitive description of these elements is partially omitted in order to avoid redundancies. In the distribution room A, air is compressed by means of a power driven compressor 40 and directed to one or more mixing chambers 51 in an air distribution network 50, which is largely separate from the water distribution network 30. There, the two distribution networks come together, water and air are mixed in the mixing chambers 51 and output from the nozzles 33.

The air in the dual-fluid secondary cooling is used for water jet atomization and at the same time for adjusting and maintaining the opening angle of the cooling jet at the nozzle 33, at different pressure settings, in particular at a low water pressure. In contrast to the "pure" water cooling of FIG. 1 The strand or slab surface is sprayed with an aerosol of very fine water droplets. The adjustment range with regard to the amount of water can thus be extended to about 1:14. The disadvantage, however, is a poor energy efficiency and consequent high investment and operating costs for the implementation of the dual-material secondary cooling, resulting in particular from the electricity and energy costs for the air compression by means of the compressor 40.

The EP 2 527 061 A1 describes a technical variant of the single-fluid secondary cooling, are used in the switching valves for intermittent opening and closing of the flow rate of a coolant. The volume flow control takes place with the help of a pulse width modulation. The use of solenoid valves and Other electronic components require a high level of maintenance and servicing, especially when used in the harsh conditions of continuous casting. In addition, in this type of flow control, the cooling effect cyclic and can lead to increased thermal stresses, which in turn can have an increased cracking in the cast product.

The JP H01 271049 A describes a secondary cooling for a continuous casting plant, in which a compressor sucks and compresses the gas, but the drive mode remains open. The GB 1 453 969 A describes a method and apparatus for continuous casting in which an electrically driven compressor compresses the gas.

Presentation of the invention

An object of the invention is to provide a device and a method for multi-material secondary cooling for a continuous casting, which overcome at least one of the above-mentioned technical disadvantages. In particular, the device and method should be energy efficient and flexible, i. ensure a large adjustment range of the volume flow and / or other parameters, and enable a safe and durable spray pattern.

The object is achieved with a device having the features of claim 1 and a method having the features of claim 9. Advantageous developments follow from the subclaims, the following description of the invention and the description of preferred embodiments.

The device according to the invention is used for multi-material secondary cooling, in particular two-component secondary cooling, for one, preferably in a continuous casting plant. The apparatus has at least one nozzle for dispensing a multi-fluid coolant onto surfaces of the cast strand. As a "cast strand" is here any cast or found casting, for example, a slab, referred to, which is subjected to a secondary cooling. In particular, it does not depend on the shape or the concrete composition of the cast product or on its processing stage, as far as it has left the casting mold. The multi-fluid coolant has at least two components, a liquid coolant and a gas. Preferably, the liquid coolant has water or is water, and preferably the gas has air or is air. In this case, the air can be used for water atomization and preferably for
Modeling and / or maintaining the opening angle of the cooling jet can be used or shared. The liquid coolant and the gas are mixed in at least one mixing chamber, which is part of the nozzle or fluidly connected to the nozzle, to the multi-fluid coolant. The apparatus further comprises a coolant distribution network, with at least one coolant line for transporting the liquid coolant to the mixing chamber and at least one control valve for controlling the volume flow of the liquid coolant to be supplied to the mixing chamber. Furthermore, the device has a gas distribution network with at least one gas line for transporting the gas to the mixing chamber. The terms "coolant distribution network" and "gas distribution network" each designate an arrangement of fluidic devices, such as lines, pipes, valves, branches, etc., which need not be arranged net like a net yet several different or a plurality of said devices must have. For the present invention, it is important that the coolant distribution network has one or more control valves for controlling the volume flow of the liquid coolant and that the two distribution networks communicate with one another at one or more mixing chambers in terms of flow. In the simplest case, the coolant distribution network has a control valve and a pipe, and the gas distribution network has a pipe.

According to the invention, the apparatus further comprises a refrigerant driven compressor having a turbine and a gas compressor. The turbine and the gas compressor are connected to each other, preferably mechanically. The compressor is configured to rotate the turbine of a portion of the liquid coolant, whereby the gas compressor sucks, compresses and supplies gas to the gas distribution network.

The refrigerant-driven compressor draws and compresses gas through a portion of the kinetic energy of the liquid refrigerant. This energy is used, which is converted in conventional systems such as the volume flow control valve in friction or flows off unused via an overflow control valve. Thus, according to the invention, this excess energy of the Liquid coolant flow used to perform the gas compression, ie energetically fully or partially support. This makes cooling more energy efficient. In addition to an improved cooling effect, the atomization of the liquid coolant by means of the gas can reduce the clogging of the nozzles by deposits, such as lime. The described secondary cooling system allows a large adjustment range and a safe and durable spray pattern. The conversion of a conventional two-fluid secondary cooling to such a liquid coolant-assisted gas compression is possible in a simple manner, because the existing line / valve / mixing chamber / nozzle architecture can be used in substantial parts. If the gas compression has conventionally been carried out by means of a power-driven compressor, this can be replaced or supplemented with the liquid-operated compressor described above.

Although fluidic relationships are often described singularly for purposes of clarity of illustration, such as with a control valve, mixing chamber, nozzle, compressor, etc., the invention and its preferred embodiments are not so limited. In an analogous and preferred manner, a plurality of control valves and / or a plurality of mixing chambers and / or a plurality of nozzles and / or a plurality of compressors and / or a plurality of pumps (see below), etc. may be provided.

Preferably, the apparatus further comprises at least one pump that pumps liquid coolant into the coolant distribution network, wherein the liquid coolant for driving the turbine is branched from a conduit section between the pump and the control valve. This splits the liquid coolant circuits for turbine operation and nozzle operation, making it possible to always run the pump at the optimum operating point with the highest performance.

Preferably, the at least one control valve is a piston valve with a ring diffuser. In particular, at a low liquid coolant consumption in the case of a piston valve, a large amount of energy of the liquid flow on Ring diffuser converted into friction, which can be profitably used for compression of the gas by means of the compressor.

Preferably, the turbine and the gas compressor are connected to each other via a transmission, whereby the flexibility of the device with regard to the compression of the gas and thus on the production of the two-fluid coolant is improved.

Preferably, the device has a gas treatment unit which has a filter and / or a dewatering device for the treatment of the gas to be supplied into the gas distribution network, wherein the gas treatment unit is in this case particularly preferably arranged in the flow direction in front of the compressor. The gas - in particular air treatment can be realized with relatively little effort, which protects the system from foreign bodies and thus increase their reliability.

Preferably, the device comprises at least one bypass valve downstream of the compressor for dividing the refrigerant toward the compressor and the nozzle, the bypass valve preferably being a self-regulating valve controlled by the applied liquid refrigerant pilot pressure and for a given gas / refrigerant Ratio at the nozzle is preset. In this way, an autonomous control or autonomous partial control of the device can be realized, in particular the compressor in this case can be used as an autonomous unit immediately in the vicinity of the continuous casting plant, e.g. on a continuous casting segment or segment support frame or on the cooling chamber wall to arrange, whereby a conventional system in a still simpler manner can be retrofitted with the present invention.

Preferably, the device has a distributor space and a continuous casting segment separated therefrom, wherein the at least one control valve and the compressor are arranged in the distributor space and the at least one nozzle is arranged in the continuous casting segment. The separation is in this case, for example, with respect to the temperature and / or purity of the atmosphere and / or moisture understand. Thus, according to this preferred embodiment, rotating or otherwise more sensitive parts are in a less harsh environment, ie, the manifold space, as compared to the continuous casting segment. This can increase the reliability of the system and reduce maintenance.

On the other hand, it may be useful, as stated above, just in terms of modularity or retrofitting, to arrange the compressor in the vicinity of the strand to be cooled, in which case it is particularly preferred that at least one control valve in the distribution chamber and the compressor and the to arrange at least one nozzle in the continuous casting segment.

The above-described object of the invention is further achieved by a method comprising: transporting a liquid coolant, preferably water, by means of at least one coolant line through at least one control valve for controlling the volume flow of the liquid coolant into at least one mixing chamber; Transporting a gas by means of at least one gas line into the at least one mixing chamber, in which the liquid coolant and the gas are mixed to form a multi-substance coolant; Dispensing the multi-fluid coolant through at least one nozzle onto surfaces of the cast strand. According to the invention, the gas is compressed by means of a compressor which is driven by a part of the liquid coolant. The technical effects and advantages of the method correspond to those described above with respect to the device.

The method is particularly preferably carried out by means of the device according to the invention or one of the described preferred embodiments.

The described devices and methods primarily serve the multi-material secondary cooling, in particular two-component secondary cooling, in a continuous casting plant. However, if appropriate, the invention can also be used in other systems, as far as multicomponent cooling is carried out.

Further advantages and features of the present invention will be apparent from the following description of preferred embodiments. The features described therein may be implemented alone or in combination with one or more of the features set forth above insofar as the features do not conflict. The following description of the preferred embodiments is made with reference to the accompanying drawings.

Brief description of the figures

• The FIG. 1 shows a schematic of a conventional water-secondary cooling for a continuous casting plant.
• The FIG. 2 shows a schematic of a conventional dual-fluid secondary cooling for a continuous casting plant.
• The FIG. 3 shows a schematic of a two-fluid secondary cooling for a continuous casting plant according to an embodiment of the invention.
• The FIG. 4 shows a water-driven air compressor suitable for use in dual-fluid secondary cooling.
• The FIG. 5 shows a schematic of a two-fluid secondary cooling for a continuous casting plant according to another embodiment of the invention.
• The FIG. 6 is a perspective view of a continuous casting segment, on its side a water-powered air compressor is mounted.

Detailed description of preferred embodiments

In the following, preferred embodiments will be described with reference to the figures. Here are the same, similar or equivalent elements with provided with identical reference numerals, and a repetitive description of these elements is partially omitted in order to avoid redundancies. This also applies with reference to the above, described in the section "Background of the Invention" Figures 1 and 2 ,

The FIG. 3 shows a schematic of a dual-fluid secondary cooling for a continuous casting plant according to an embodiment.

Unlike the one in the FIG. 2 shown conventional dual-fluid secondary cooling system excess water energy, which has dropped, for example, the overflow control valves 34, used to drive a water-driven air compressor 60, more precisely, a turbine 61 of the compressor 60. The compressor 60 may, for example, a turbine 61, which is designed according to the basic principle of a Francis turbine.

In the present embodiment, the compressor 60 is disposed in the distribution room or media room A to utilize the energy of the excess water to compress air, which is then supplied via the air distribution network 50 to the mixing chambers 51 of the nozzles 33. For this purpose, the excess water sets a water wheel in the turbine 61 of the compressor 60 in rotary motion. A possible component of the compressor 60 may be a torque converter for the low-impact starting. The rotational movement of the water wheel is forwarded directly or with the aid of a gear 62 to an air compressor 63. The air compressor 63 is part of the compressor 60 and may be designed, for example, as an axial or radial compressor or side channel compressor. The air compressor 63 sucks in the air via an air conditioning unit 64 having, for example, a filter and / or a dewatering device and places the air in the air distribution network 50.

The FIG. 4 FIG. 12 shows an exemplary water powered air compressor 60 suitable for use with the dual-fluid secondary cooling described. In addition to the components mentioned, ie the turbine 61, the air compressor 63 and the direct Connection or the gear 62 in between, shows the FIG. 4 a water supply port 65 and a water drain port 66, and an air suction port 67 and an air discharge port 68, through which the air compressed by the air compressor 63 is discharged into the air distribution net 50.

By the water-driven (or generally coolant-driven) compressor 60, air is sucked in and compressed by excess water energy. Thus, the energy of the water flow, which has been converted into friction in conventional systems on the volume flow control valve 31 or flowed off via the overflow control valve 34 unused, can be used to energetically fully or at least partially support the air compression. By splitting the water circuits for turbine operation and nozzle operation, it is possible to always drive the water pump (s) 20 at the optimum operating point with the highest power, i. at the maximum of the pump characteristic curve, which describes the relationship between the volume flow delivered by the pump and the pressure built up by the pump. According to the illustrated embodiment, the rotating parts are in the unproblematic environment of the distribution chamber, unproblematic in terms of air cleanliness, humidity and / or temperature. The air treatment and / or filtering by means of the air treatment unit 64 can be realized with relatively little effort.

The terms "water distribution network" or "coolant distribution network" and "air distribution network" or "gas distribution network" each designate an arrangement of fluidic devices, such as pipes, pipes, valves, branches, etc., which need not be arranged in the strict sense net or more must have different or a plurality of said facilities. The lines for transporting the water and the air according to the embodiments shown in detail go from the FIGS. 1, 2 . 3 and 5 schematically, even if they do not bear the reference numerals for clarity.

The FIG. 5 shows a schematic of a two-fluid secondary cooling for a continuous casting plant according to another embodiment.

According to this embodiment, the compressor 60 as an autonomous unit is immediately adjacent to the continuous caster, e.g. in the continuous casting segment C or on the segment support frame or on the cooling chamber wall. The unit includes a turbine 61, an air compressor 63, an optional transmission 62, an optional torque converter (not numbered), an air conditioning unit 64, and a bypass valve 69. The bypass valve 69 may be self-regulating, for example by being controlled by the applied water pressure. The bypass valve 69 may be preset at the nozzle 33 for a given air / water ratio. In order to be able to ensure the variance of the pending water pre-pressure at the bypass valve 69, it is preferable to use a part of the original setting range, for example 80 to 100% of the stroke.

Compared to the embodiment of FIG. 3 can in the autonomous embodiment of the FIG. 5 the piping costs are kept lower. For example, the cost of materials, assembly costs and the downtime for the assembly of the air lines are lower. That goes also from the FIG. 6 showing a continuous casting segment on the side of which a water driven air compressor 60 is mounted. In contrast, there are rotating or sensitive mechanical parts compared to the embodiment of FIG. 3 in a harsher environment (possibly casting powder and / or vapor in the atmosphere, radiating strand, high temperatures) since they are arranged in the continuous casting segment C.

Where applicable, all individual features illustrated in the embodiments may be combined and / or interchanged without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

10

reservoir

20

Pump / water pump

30

Water distribution system / coolant distribution system

31

control valve

32

Valve control / flow meter

33

jet

34

About flow control valves

35

scale flume

40

Electric compressor

50

Air distribution grid / gas distribution network

51

mixing chamber

60

coolant driven compressor

61

turbine

62

transmission

63

Air compressor / gas compressor

64

Air conditioning unit / gas processing unit

65

Water supply port

66

Water drain port

67

air intake port

68

Air discharge port

69

Bypass valve

A

Distribution space / Media Room

B

piping

C

Segment of the continuous casting plant where secondary cooling takes place

Claims (10)

1. Device for multi-substance secondary cooling for a continuous casting plant, wherein the device comprises:

   at least one nozzle (33) for delivery of a multi-substance coolant to surfaces of the cast strip;

   at least one mixing chamber (51), which is part of the nozzle (33) or connected with the nozzle (33) in terms of flow and in which liquid coolant, preferably water, and a gas, preferably air, are mixed to form the multi-substance coolant;

   a coolant distributor network (30) with at least one coolant line for transport of the liquid coolant to the mixing chamber (51) and at least one regulating valve (31) for regulating the volume flow of the coolant to be fed to the mixing chamber (51); and

   a gas distributor network (50) with at least one gas line for transport of the gas to the mixing chamber;

   characterised in that

   the device comprises a coolant-operated compressor unit (60) with a turbine (61) and a gas compressor (63) connected therewith, wherein the compressor unit (60) is so arranged that the turbine (61) is set into rotation by a part of the liquid coolant whereby the gas compressor (63) inducts and compresses gas and feeds it to the gas distributor network (50).
2. Device according to claim 1, characterised in that this comprises at least one pump (20) which pumps the liquid coolant into the coolant distributor network (30), wherein the liquid coolant for driving the turbine (61) is branched off from a line section between the pump (20) and the regulating valve (31).
3. Device according to claim 1 or 2, characterised in that the at least one regulating valve (31) is a piston valve with a ring diffusor or a V-ball valve without a ring diffuser.
4. Device according to any one of the preceding claims, characterised in that the turbine (61) and the gas compressor (63) are connected together by way of a transmission (62).
5. Device according to any one of the preceding claims, characterised in that this comprises a gas preparation unit (64) which has a filter and/or a water removal device for treatment of the gas to be fed into the gas distributor network (50), wherein the gas preparation unit (64) is preferably arranged upstream of the compressor unit (60) in flow direction.
6. Device according to any one of the preceding claims, characterised in that this comprises at least one bypass valve (69), which is upstream of the compressor unit (60) in flow direction, for apportioning the coolant to the compressor unit (60) and the nozzle (33), wherein the bypass valve (69) is preferably a self-regulating valve which is controlled by the adjacent liquid coolant entry pressure and is preset for a predetermined gas/coolant ratio at the nozzle (33).
7. Device according to any one of the preceding claims, characterised in that this has a distributor chamber (A) and a continuous casting segment (C) separate therefrom, wherein the at least one regulating valve (31) and the compressor unit (60) are arranged in the distributor chamber (A) and the at least one nozzle (33) is arranged in the continuous casting segment (C).
8. Device according to any one of claims 1 to 6, characterised in that this has a distributor chamber (A) and a continuous casting segment (C) separate therefrom, wherein the at least one regulating valve (31) is arranged in the distributor chamber (A) and the compressor unit (60) and the at least one nozzle (33) are arranged in the continuous casting segment (C).
9. Method for multi-substance secondary cooling in a continuous casting plant, wherein the method comprises:

   transporting a liquid coolant, preferably water, by means of at least one coolant line through at least one regulating valve (31) for regulation of the volume flow of the liquid coolant into at least one mixing chamber (51);

   transporting a gas by means of at least one gas line into the at least one mixing chamber (51), in which the liquid coolant and the gas are mixed to form a multi-substance coolant; and

   delivering the multi-substance coolant through at least one nozzle (33) onto surfaces of the cast strip;

   characterised in that

   the gas is compressed by means of a compressor unit (60), which is driven by a part of the liquid coolant.
10. Method according to claim 9, characterised in that this is realised with a device according to any one of claims 1 to 8.

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