Device and method for managing heat exchange in a crystallizer

Abstract

The present invention relates to a device for controlling heat exchange in a crystallizer (26, 126, 226, 326), in which there are cooling channels (48, 148, 348) and one or more temperature sensors (154, 158, 160, 260, 360) that are placed at the outlets (148b, 248b) of the channels and / or inside the channels and measure the temperature of the cooling fluid, e.g., at different values ​​T at the outlets of the various channels. OUT The temperature difference ΔT between the crystallizer and the associated ingot mold (227) is calculated to identify any unevenness in the heat exchange during casting. The outlet temperature sensor can be located around the crystallizer itself or around the cover (272, 372a, 372b) closing the gap (271) between the crystallizer and the associated ingot mold (227). An associated cover with an associated kit, an associated casting plant, a method for controlling the heat exchange, and the use of the device to replace the crystallizer are also described.

Description

[Technical Field]

[0001] The solution relates to a device and a method for monitoring the trend and uniformity or non-uniformity of heat exchange in a crystallizer, which can be used in continuous casting processes of long products such as billets, blooms, beam blanks, or flat products such as regular plates or slabs. [Background technology]

[0002] Crystallizers are well known and fundamental components in the field of continuous casting: they have the function of giving shape to the product that is cast inside them, and by heat exchange they define the shape and thickness of the skin of the product itself.

[0003] In practice, molten steel is poured into a crystallizer, which extracts heat from the steel by cooling it internally with a liquid, transferring the heat to the cooling fluid and causing the gradual formation of a skin, which must be thick enough to contain the stationary molten steel inside without continuously trapping it at the exit from the crystallizer.

[0004] Crystallizers can have a variety of shapes suitable for casting flat or long products. They can be constructed as a single piece, typically for long products, or as modular pieces, typically for flat products. They can have a variety of dimensions, e.g., internal widths starting from 110 mm to 1600 mm, and even larger for vertical casting of billets. For flat products, crystallizers can even have internal widths greater than 2000 mm, while thicknesses generally do not exceed 400 mm.

[0005] All the crystallizers mentioned are connected to a closed circuit to allow heat to be extracted from the steel and to withstand the high operating temperatures, which cools the crystallizer by circulating a cooling fluid, generally water.

[0006] First-generation crystallizers consisted of tubes with a specific thickness, fitted into special chambers called conveyors, which created a gap, also called an aperture, between the outside of the tube and the inside of the conveyor, the whole fitted into an ingot mold. A cooling fluid, e.g., below room temperature, entering from one side was then introduced into this conveyor and withdrawn warm on the other side, cooling the tubes contained in the conveyor along its path.

[0007] An evolution of this concept envisaged perforating the interior of the crystallizer longitudinally to create through channels through which a cooling fluid could be passed, which allowed for a subsequent increase in the casting speed as the skin formed more rapidly.

[0008] Furthermore, given the difficulty of creating transverse holes to limit manufacturing costs, the concept has been extended to creating cooling channels by externally rolling the crystallizer walls, and their final definition through closures, preferably with carbon fiber panels and / or windings, as described, for example, in EP 3013498. This crystallizer variant makes it possible to have thinner crystallizer walls compared to versions with through-channels.

[0009] The above-mentioned crystallizer developments make it possible to improve the heat exchange and reduce the manufacturing costs of the crystallizer, especially by switching to a cooling principle with through-channels or externally created channels; the heat exchange in the corners of this crystallizer can be adjusted.

[0010] Typically, each channel is provided with a common flow and the fluids flowing through the crystallizer are drawn from a common manifold.

[0011] However, the casting process, while being carried out, hides several unknowns, and the mechanism of skin formation can inadvertently result in an inappropriate configuration: in fact, the support of the skin formed on the crystallizer wall may not be optimal; hot or cold spots may appear in the crystallizer, which is of insufficient thickness, or may detach from the crystallizer, which no longer exchanges heat properly, with the risk that the uncooled skin will melt due to the heat of the steel inside and / or resolidify, causing quality defects; or even exit the crystallizer with an insufficient thickness, with the risk of tearing due to the static pressure of the molten metal, resulting in a so-called breakout, i.e. a leak of molten steel that interrupts the process, with subsequent production losses, potentially damaging the plant and potentially risking the safety of the operators.

[0012] It is therefore important to be aware of the status and development of heat exchanges during the continuous casting process, thereby identifying any potential thermal imbalance in time before it leads to potentially harmful phenomena such as skin breakdown (so-called breakouts) or quality defects in the product, which need to be identified as early as possible in order to eliminate the cause or at least mitigate its effects.

[0013] In this regard, the prior art includes systems for measuring temperature trends in crystallizers. European Patent Application Publication No. 3668665 and International Patent Application Publication No. 2020 / 254688 are cited as examples. They describe crystallizers in which channels or grooves perpendicular to the casting direction are provided in the walls, including sensors for monitoring the temperature distribution in the crystallizer. These systems are complex and expensive, exposing the temperature sensors to high temperatures inside the walls of the crystallizer. Other documents describing systems for monitoring temperature trends in crystallizers are European Patent Application Publication No. 4023359, Korean Patent Publication No. 2001-0017893, and Korean Patent Registration No. 10-0399233. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] European Patent No. 3013498 [Patent Document 2] European Patent Application Publication No. 3668665 [Patent Document 3] International Publication No. 2020 / 254688 [Patent Document 4] European Patent Application Publication No. 4023359 [Patent Document 5] Korean Patent Publication No. 2001-0017893 [Patent Document 6] Korean Patent No. 10-0399233 Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention aims to overcome the above-mentioned drawbacks and to propose a reliable and at the same time not very complex device and associated method for controlling heat exchange in a crystallizer. Another aim of the present invention is to reduce the manufacturing costs of the crystallizer and the associated costs for managing a continuous casting plant, minimizing accidents during casting and quality defects in the products.

[0016] Other objects and advantages of the present invention will become apparent from the following description. [Means for solving the problem]

[0017] In a first aspect of the present invention, the object is achieved by a device for controlling heat exchange in a crystallizer, the device comprising: (a) a crystallization unit comprising: (a-1) A crystallizer for continuous casting, (a-1.1) a tubular body with at least one wall defining a longitudinal through-hole; (a-1.2) a plurality of first cooling channels, preferably longitudinal, with one end serving as an inlet and the other end as an outlet; a crystallization unit comprising a crystallizer having (b) one or more first temperature sensors; - the temperature T at the associated outlet of the cooling fluid located at the outlet of the first cooling channel and flowing through the first cooling channel during use of the crystallizer; OUT Measure and / or one or more respective temperatures T located at different heights, preferably N, inside the first cooling channel along its longitudinal extension, corresponding to different heights of the cooling fluid flowing through the first channel during use of the crystallizer; N To measure a first temperature sensor; If there is only one temperature sensor, the only temperature sensor is a multi-point sensor.

[0018] The term "cooling channel" means a channel passing through at least one wall and a groove obtained in at least a part of the outer surface of said at least one wall, each covered by a cover.

[0019] The term "through channel" means a channel perforated in the wall of the crystallizer, closed along its longitudinal extension by the wall itself, with openings only at the ends. In contrast, "groove" refers to a recess provided on the outer surface of the wall of the crystallizer, which is open to the outside along its longitudinal extension. Covering this longitudinal opening results in a closed channel on its longitudinal sides, with openings only at both ends, i.e., at the inlet and outlet of the channel.

[0020] The term "tubular" refers to a tube, and thus a hollow elongated body, with cross-sections of various geometries, such as circular, rectangular, polygonal, H-shaped, etc. This list is not exhaustive.

[0021] The preferred extension of the cooling channels is longitudinal, following the course of casting and therefore the course of solidification and cooling of the metal involved in its movement through the crystallizer. Extensions that are not parallel to the casting direction, such as transverse or oblique extensions, are also conceivable.

[0022] The definition of "at the outlet of the channel" does not only refer to a position directly corresponding to the actual outlet of the cooling channel, but also to an inner or outer position at the end of the cooling channel, and can be considered to be the same as a distance of the temperature measuring sensor to the actual outlet, preferably less than 10 cm, more preferably less than 4 cm, and even more preferably less than 2 cm.

[0023] In the case of grooved crystallizers, the outlet position can be located in the end zone of the groove that is not closed by the respective cover. In the case of temperatures measured at the outlet of the channel, and therefore in the outlet zone, the temperature value is taken as T OUT It can be said that:

[0024] Positioning the first sensor at the outlet of the cooling channel of the crystallizer results in a less complex system than prior art crystallizers, which provide dedicated systems or channels for cooling the crystallizer and for measuring the temperature conditions in the crystallizer. Additionally, temperature sensors directly affected by the flow of cooling fluid are exposed to lower temperatures than sensors inserted in channels made inside the crystallizer wall. This is assumed by prior art, such as EP 4023359, which is adapted to measure the temperature of copper in contact with steel, rather than the temperature of the cooling fluid in the present invention.

[0025] Outlet temperature T OUT The comparison between the measurements of T, i.e. between the temperature sensors present only at the outlet of the cooling channels, already provides information on the temperature difference between said channels and indicates irregularities in the heat exchange in the crystallizer. OUTIt is suggested that the control unit may comprise a control unit configured to receive the values ​​and calculate the difference between them. Comparison with the input temperature is not necessarily necessary to obtain sufficient information about the temperature trend in the crystallizer measuring the temperature at the outlet of the channel and therefore the temperature at the same height at the end of the crystallizer.

[0026] Any identified occurrence of temperature non-uniformity or irregularity will be utilized using the characteristics of the above-mentioned state-of-the-art crystallizers, in which separate cooling channels are provided, and the temperature increments ΔT occurring between the cooling fluid flows of the different cooling channels will be monitored and then compared, for example, the temperature increments ΔT being of the same magnitude, as explained below, or even within individual cooling channels.

[0027] Periodic, or better still, continuous, monitoring of this temperature increment ΔT will make it possible to identify any peaks or drops in local heat exchange in the temperature trend of the monitored channel in time, thereby making it possible to understand which zones in the crystallizer are most at risk and to take appropriate measures in time. This monitoring is the object of another aspect of the invention, which is shown below.

[0028] In a preferred embodiment of the present invention, the heat exchange control device according to the present invention further comprises: (c) the inlet temperature T of a cooling fluid located upstream of the first cooling channel and flowing through the first cooling channel during use of the crystallizer. IN at least one second temperature sensor measuring Equipped with.

[0029] The at least one second temperature sensor can be located outside the crystallizer or can be located in the entrance zone of the cooling channel of the crystallizer.

[0030] The term "at the inlet" is to be understood mutatis mutandis as "at the outlet" as defined above.

[0031] Reading and comparing the inlet temperature (possibly a common temperature for all cooling channels) and the outlet temperature of at least one, or preferably some, and more preferably all, of the cooling channels helps to understand the intensity of cooling occurring in the crystallizer. The inlet temperature is generally in the range of 10-50°C, preferably in the range of 20-40°C (room temperature).

[0032] Comparison with the inlet temperature is also possible without measuring it with a temperature sensor, since the device according to the invention may be equipped with a system for setting it to the desired value.

[0033] In one embodiment of the invention, the crystallization unit further comprises a cooling fluid source, in particular a cooling system or circuit connected to the first cooling channel and feeding cooling fluid through its inlets.

[0034] It goes without saying that the device according to the invention may comprise a control unit which receives the various measured temperature data and calculates the desired temperature difference, but which may also read the temperature values ​​indicated by the sensors by the operator and take into account and evaluate the individual values.

[0035] In another embodiment of the present invention, the heat exchange control device comprises: (d) a control unit, (d-1) Outlet temperature of each cooling channel T OUT and / or receive from the first sensor a measurement signal of the temperature T at various heights of the crystallizer. N to receive the measurement signal; (d-2) Optionally, if at least one second temperature sensor is present, a temperature T IN to receive the measurement signal; (d-3) calculate the temperature difference ΔT among the received temperature values; and (d-4) processing commands for controlling the casting parameters of the continuous casting plant equipped with a crystallizer based on the calculated value ΔT; The device further comprises a control unit configured to:

[0036] The temperature T measured at the outlet between different channels, for example adjacent or opposite channels OUT The differences ΔT indicate different temperatures of the cooling fluid inside the channels, and therefore also indicate differences between the heat exchanges taking place between the crystallizer and the steel. A person skilled in the art will use his general knowledge to identify the analyzed differences ΔT in order to obtain information on the heat exchanges in the crystallizer.

[0037] Preferably, if there are sensors located at different heights of the cooling channels, it is possible to calculate different values ​​of ΔT between the various measurement points in each cooling channel, providing a more detailed mapping of the temperature distribution in height, position and extension for cooling non-uniformities in the crystallizer. The more sensors are provided inside one or more channels and / or at the outlet of one or more channels, the more correction of the cooling or casting itself can be achieved.

[0038] For more useful information, see T N or T OUT and T IN can be obtained by calculating the temperature difference between the

[0039] The number of sensors can be reduced to reduce manufacturing and economic costs. In a preferred embodiment of the present invention, the crystallizer is divided into several sections. Each section is assumed to have a certain number of first cooling channels. For each section, several first temperature sensors are provided, the number of which is less than the number of cooling channels. Some sensors can be zeroed in some sections, for example, by alternating sections with and without sensors. Therefore, the presence of several first temperature sensors positioned at the outlets of the first cooling channels and / or within the first cooling channels does not mean that all outlets of the channels or all interiors of the channels are equipped with temperature sensors.

[0040] For example, it is possible to divide the circumference of the crystallizer into quadrants, provide at least one outlet sensor in each quadrant, and compare quadrants between them, which would result in less precision in the measurement, but would require less investment in installed equipment and maintenance / replacement.

[0041] As described elsewhere in this specification, it is also clear that there can be multiple sensors per channel without departing from the scope of protection of the present invention. The temperature sensors used can be of various types. In one embodiment of the present invention, the temperature sensor among the multiple sensors is a single-point sensor, preferably selected from thermocouples and thermal resistors. The single-point sensor or transducer makes it possible to obtain a signal over time, thereby making it possible to monitor the temperature trend of the casting.

[0042] The capture frequency may be, for example, 1 Hz, but may be increased or decreased as required. This applies to all embodiments.

[0043] To improve the reliability of the temperature detection system, the number of cables to be managed is limited. It is possible to consider adopting a multipoint measurement system, for example optical fibers. In this regard, in another preferred embodiment of the invention, the temperature sensor is a multipoint sensor, preferably a Bragg grating optical fiber. Optical fibers with several measurement points allow temperature mapping along the cooling channel, or in one or more annular arrangements, or along the periphery, as will be shown below. In the zone at the exit from the channel, these fibers always have a temperature of T OUT It also makes it possible to measure

[0044] Within this embodiment of the invention, two sub-variants are conceivable: the first, in which the optical fibers are inserted longitudinally in (at least some) channels of the crystallizer, and the second, in which the optical fibers are in a horizontal position, which also allows for a placement along the periphery of the crystallizer. For example, in crystallizers for flat products, where sensors are provided only on some of the plates forming the crystallizer, a horizontal placement is also conceivable, which does not affect the entire periphery at the end of the crystallizer.

[0045] An optical fiber typically contains a number of reflective (measurement) points at equal distances, which, when subjected to temperature variations, undergo deformations that alter the range of dimensions of the optical fiber and therefore the range of its reflective capabilities. Depending on these variations, it is possible to determine the value of the temperature detected by the reflective points. The use and operation of Bragg fibers are known to those skilled in the art and need not be described in further detail.

[0046] In an advantageous embodiment of the invention, a multipoint temperature sensor is inserted in the longitudinal direction of at least one of the first cooling channels, thus parallel to the casting direction, in which case the measuring points at the ends of the cooling channels measure the temperature values ​​T OUT The insertion of a vertical fiber in the cooling channel can be combined with the presence of a sensor in front of the outlet of the channel, in which case the value TOUT corresponds to the value of the sensor placed in front of the outlet of the channel.

[0047] For example, it is possible to create an additional channel inside the crystallizer, inside the cooling channel, for setting the optical fiber. Once inserted, the optical fiber is fixed using a paste that allows for slight deformation, for example a silicone-based paste.

[0048] By measuring the temperature with various fibers passing through the cooling channels of the crystallizer, it is possible to compare the temperature distribution along all the walls of the cooling channels as the solidification progresses. By comparing the readings of several channels, it is possible to determine if there are zones with hot or cold spots and to intervene.

[0049] With regard to the number and positioning of the temperature sensors, the control device according to the invention can be divided into several variants.

[0050] In a first variant, it is possible to insert a first temperature sensor or transducer with a single measurement point, for example at the outlet from the cooling channel. By applying multiple sensors, i.e., multiple-channel transducers, it is possible to compare these values ​​ΔT and see if there are any relevant differences, which are indicative of any disturbances in the crystallizer.

[0051] Considering an example with a crystallizer with 52 channels, 52 sensors or transducers would be needed at the fluid outlets for at least one complete reading, but there is no problem in inserting multiple sensors at the inlets as well, even if this increases the setup cost.

[0052] Another arrangement is that already described, longitudinal or vertical (parallel to the casting direction) inside one or more cooling channels.

[0053] In another embodiment of the invention, the heat exchange control device comprises a plurality of single-point sensors, or in a particularly advantageous manner, at least one multi-point sensor, which are positioned around the end of the crystallizer and at the outlet of the first cooling channel, whereby the sensors are affected by the flow of cooling fluid at the outlet of the first cooling channel. The arrangement along or around the periphery of the crystallizer is simplified, in particular by using optical fibers, which allow the simultaneous measurement of the values ​​T of several channels. OUT This configuration allows for the integration of the above components and has a simple structure.

[0054] A particularly simple construction advantageously provides that the crystallizer further comprises a circumferential cavity at the end, thus in the outlet zone of the first cooling channel, which accommodates a plurality of single-point sensors or at least one multi-point sensor. This circumferential cavity can be located in the side wall of the crystallizer or on the edge of the crystallizer. This circumferential cavity is preferably groove-shaped and can be suitably covered to accommodate the sensors, but can also be a through-channel communicating with the first cooling channel.

[0055] Advantageously, T IN The system measures the temperature of the cooling fluid at the inlet to the crystallizer, T IN It can be integrated with sensors that detect

[0056] A particularly advantageous embodiment of the invention relates to a horizontal arrangement of sensors, i.e. of the relevant temperature measuring points, which are positioned around the periphery of the crystallizer but are removable therefrom. Such an embodiment is advantageous when the crystallization unit: (a-2) an ingot mold into which the crystallizer is inserted; (a-3) a first cover, preferably disk-shaped, adapted to close the gap between the crystallizer and the ingot mold, with a central opening complementary to the outlet of the crystallizer; (a-3.1) a plurality of second channels arranged radially around the opening, which are continuous with the first cooling channel when the gap is in a closed state using the first cover; (a-3.2) a cavity, preferably annular, extending around the central opening, communicating with the second channel and housing one or more first temperature sensors, in particular multi-point sensors; a first cover having Further provided are:

[0057] The cavity may also be a composite of multiple single cavities to contain individual temperature sensors.

[0058] To further cool the crystallizer, it is advantageous to fill the ingot mold with cooling fluid by introducing water into the crystallizer channel inserted directly into the ingot mold. Advantageously, the distance of the single-point sensor or the distance of the measuring points in a multi-point sensor substantially corresponds to the distance of the second channel in the cover. Therefore, the peripheral arrangement of the sensor around the opening of the crystallizer can be made directly on the crystallizer or on a separate element, i.e., on a closing element, i.e., on the cover, in an associated peripheral or annular cavity, with a peripheral cavity. In other words, a horizontal arrangement on the cover can be described as a transverse arrangement, i.e., perpendicular to the casting direction.

[0059] The type of "vertical" temperature measurement, i.e., along the cooling channel, as can be seen above, represents an accurate but very complex system. It certainly provides a lot of data, but it inevitably involves a deterioration (with the associated burden and costs) in terms of the number of sensors to be installed. Furthermore, it is not easy to create and plug sensors in the channel, and the additional process to accommodate the fibers is expensive, especially in small tubular crystallizers.

[0060] In particular the use of sensors with multiple measuring points, in particular the use of optical fibres, and more particularly horizontal positioning in the periphery, makes it possible to realise a device for measuring the temperature of a cooling fluid that gives good results in terms of data acquisition, but at the same time makes the setup process easier and more economically sustainable.

[0061] As confirmed above, setting the fiber horizontally means positioning the fiber near the hole at the exit from the cooling channel, and it is noted that advantageously the sensor or optical fiber reflection point is positioned at the front of the channel, so that it is hit by the flow of warm water exiting the crystallizer over time. The term "peripheral" refers to placement around or along the periphery of the crystallizer.

[0062] In this way, the signals detected by the reflecting points can be acquired to monitor, in particular, the temperature variations of the individual channels starting from a common inlet temperature in the various cooling channels.

[0063] A preferred embodiment of the present invention solves the problem of fixing the sensor, and in particular the optical fiber, to the first cover, avoiding the application of fixing means such as glue, silicone paste or fasteners: it is envisaged that the first cover comprises a plurality of second channels in the form of grooves and a preferably annular cavity in the form of a groove as defined above. (a-4) A second cover, (a-4.1) preferably disk-shaped, with a central opening adapted to close the gap between the crystallizer and the ingot mold and complementary to the outlet of the crystallizer; (a-4.2) between the first and second covers, the first cover is compatible with the first cover so as to cover the one or more temperature sensors and close the second groove; It is envisioned that a second cover may also be provided.

[0064] Advantageously, the second cover comprises a plurality of third grooves radially arranged around the opening and a cavity, preferably annular, extending around the central opening. The arrangement of the second and third grooves, and preferably the arrangement of the cavities, is mirrored in the cover so that, when the gap is closed using the first and second covers, the second and third grooves, like the corresponding cavities, form closed channels. It is particularly advantageous to use a component for closing the cooling channel, which is adapted to at least partially connect with one end of the crystallizer. This component is generally grooved, and a special space, such as an annular cavity for setting an optical fiber, is also created therein. As indicated above, this closing component can also be made as two or more bodies adapted to surround one or more fibers therebetween and connect with each other. In addition to annular cavities, other shapes of cavities are also conceivable for accommodating sensors.

[0065] This configuration is particularly advantageous because the fiber is enclosed between the closing components (covers), leaving only a small area exposed to the flow of cooling fluid, and is not subjected to dangerous vibrations that can interrupt the reading and lead to premature wear of the fiber over time.

[0066] In the case of optical fibers inserted into the first cooling channel, a cover with a through channel or groove for the fiber to pass through as it exits the crystallizer can also serve to occlude the fiber.

[0067] A second aspect of the present invention relates to a cover for closing the gap between an ingot mold and a crystallizer inserted therein, the cover preferably being disc-shaped and having a central opening that is complementary to the outlet of the crystallizer, the cover being (i) a plurality of channels radially disposed around the opening, the opening being in a gap-closed state with a first cover, and aligned with cooling channels present in the crystallizer; and (ii) a cavity, preferably annular, extending around said central opening and preferably connected to said radial channels, adapted to accommodate one or more temperature sensors, in particular multi-point sensors, in particular Bragg grating optical fibers; and optionally (iii) one or more temperature sensors, in particular multi-point sensors, in particular Bragg grating optical fibers, inserted into said cavity; Equipped with.

[0068] The channels may be through channels or grooves cut into the surface of the cover.

[0069] As an alternative to an annular cavity, there may be cavities of other shapes adapted to accommodate sensors in the zones of the channels / grooves.

[0070] As mentioned earlier, the crystallizer is located inside the ingot mold, allowing for the installation of a conveyor, thereby enabling the connection of a cooling supply and return; the crystallizer is a consumable item that is replaced after a certain number of castings, but the ingot mold (and any conveyor) can be recovered, making it ideal for installing the fiber that is part of the component in the component, or in a separate component so that it can be used with several crystallizers. Using a preferred embodiment of the present invention to install a sensor in the closure element (cover) makes it easy to replace the crystallizer without having to replace or discard the sensor. Because the cover is easy to manufacture, it is economically advantageous to manufacture a cover with an integrated temperature measurement system (for example, using 3D printing).

[0071] The crystallizers can have various extensions and cross sections (circular, square, rectangular, polygonal, e.g., octagonal, H-shaped, or combinations thereof, and others), and various shapes of cast products can be produced, such as circular, square, rectangular, polygonal profiles, joined curved frames, H-shaped, etc. The present invention is not dependent on the shape of the crystallizer or the shape of the cast product.

[0072] The heat exchange measurement system integrated into the cover of the ingot mold can be easily adapted to various crystallizers.

[0073] The present invention provides, in another aspect, a cover, comprising: (i) a plurality of covers according to the present invention, adapted therebetween to close the gap between the crystallizer and the ingot mold and to enclose a temperature sensor therebetween; and / or (ii) a plurality of covers according to the present invention, each having different shapes and / or dimensions and compatible with different types of crystallizers; Equipped with.

[0074] Another aspect of the invention relates to a continuous casting plant equipped with a heat exchange control device according to the invention.

[0075] The concept of the present invention can be applied to crystallizers for flat products, generally having a substantially rectangular outlet shape, or for elongated products having a variety of more specific shapes, such as those listed above as exemplary shapes.

[0076] Another aspect of the present invention relates to a method for controlling heat exchange in a crystallizer, comprising the steps of: (I) providing the crystallizer with preferably longitudinal cooling channels applied to at least one wall of the crystallizer; (II) introducing a cooling fluid into the cooling channels, the flow of which is preferably parallel to the casting direction, the cooling fluid preferably having a common inlet temperature T IN and performing casting through a crystallizer; (III) The temperature of the cooling fluid at the outlet (T OUT ) for the plurality of cooling channels, and / or measuring the temperature of the cooling fluid (T) along the cooling channel for at least one, but preferably a plurality, of the cooling channels. N ) measuring the (IV) Temperature T at the entrance to the cooling channel IN optionally measuring or determining; (V) A step of calculating, preferably for all channels provided with temperature sensors, the temperature difference ΔT is (V-1) At least two outlet temperatures T in two different cooling channels OUT Between; (V-2) between two temperatures measured at different heights of the cooling channel or between two temperatures measured at the same height but in different cooling channels; and optionally, (V-3) Inlet temperature of the cooling channel, T IN and outlet temperature T OUT Between; (V-4) Inlet temperature T IN and the outlet temperature along the cooling channel, T N Between Calculating: (VI) identifying irregularities in the value ΔT; and (VII) correcting a casting parameter, such as, for example, casting speed or oiling, based on the irregularity determined in step (VI).

[0077] The measurements and calculations are preferably performed as a function of time. If the control of the heat exchange is limited to monitoring the temperatures and their differences, step (VII) can be omitted; if the control extends to the management of continuous casting, step (VII) is also performed.

[0078] As already mentioned above, other temperature differences can be inferred, which are obtained by using the data T OUT , T N , and optionally T INFrom this, the value ΔT can be calculated and is useful for determining irregularities that can be identified by an expert. In particular, a somewhat prolonged increase or decrease in the "normal" value indicates insufficient or excessive cooling, respectively, in a particular zone of the crystallizer. As an alternative to the method involving calculations according to (V-1) and (V-2), a method using only calculations according to (V-3) and / or (V-4) can be considered.

[0079] The method is advantageously carried out using a heat exchange control device according to the invention.

[0080] A final aspect of the invention relates to the use of a heat exchange control device in a crystallizer with a cover, which is a closing element according to the invention, in a continuous casting process with measuring the heat exchange of the crystallizer: (α) the worn crystallizer is replaced with a new crystallizer; or (β) The crystallizer is replaced with a crystallizer having another shape and / or other dimensions, so that the first cover is replaced with a new cover adapted to the shape and / or dimensions of the new crystallizer and to the respective gap created between the new crystallizer and the ingot mold.

[0081] Step (α) is possible by servicing the heat exchange control system without having to discard the heat exchange control system or provide it for a new crystallizer.

[0082] The term "alternative shape" includes the geometric shape (dimensions, cross section), but also the number and configuration of the cooling channels.

[0083] Features and advantages described with respect to one aspect of the invention may be transferred, mutatis mutandis, to other aspects of the invention.

[0084] The industrial applicability is clear when it becomes possible to solve the technical problem initially stated and to provide a device and method for controlling the heat exchange in a crystallizer, which is reliable, less complex, economical, in some embodiments imposes a lower thermal burden on the sensors used, and in some cases improves adaptability when the measurement system is removed from the crystallizer itself, making it easier to change the type of crystallizer inside the ingot mold. Thus, the present invention achieves the objectives initially stated.

[0085] Objects and advantages will be further emphasized in the disclosure of preferred examples of embodiments of the invention, given by way of non-limiting example only.

[0086] Variants and further features of the invention are the subject of the dependent claims. The description of preferred embodiments of the device, cover, kit, method, plant and use according to the invention is given by way of example, and by way of non-limiting example, with reference to the accompanying drawings. In detail, unless otherwise specified, the number, shape, size and material of the system and individual components may vary. Equivalent elements may be applied without departing from the concept of the invention. [Brief explanation of the drawings]

[0087] [Figure 1] FIG. 1 illustrates the principle of heat exchange control in a crystallizer for long products according to the present invention. [Figure 2] FIG. 1 illustrates the principle of heat exchange control in a crystallizer for flat products according to the present invention. [Figure 3] FIG. 1 represents an embodiment of a crystallization unit according to the invention with the crystallizer without the cover for horizontal placement of the temperature sensor. [Figure 4] FIG. 4 is a view of FIG. 3 with the cover attached. [Figure 5] 5 is an enlarged view of the cover of FIGS. 3 and 4, with an optical fiber provided therein; FIG. [Figure 6]1 is a diagram illustrating the trend of the value ΔT as a function of time under various embodiments, where ΔT is understood to be the difference between various values ​​of TOUT. [Figure 7] FIG. 10 depicts temperature trends for a crystallizer with vertical optical fibers. [Figure 8] 1 shows a schematic diagram of an embodiment of the positioning and fixation of the optical fiber at the end of the crystallizer. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0088] The principles of temperature measurement in crystallizers and adjustment of the casting system are shown in Figures 1 and 2. These are differentiated by the type of crystallizer: a crystallizer for long products in Figure 1 and a crystallizer for flat products in Figure 2. For purely illustrative purposes of the crystallizer, various possible positions for the temperature sensor are shown, which do not necessarily have to be simultaneous.

[0089] In Figure 1, the crystallizer 126, which in the example is cylindrical, is provided with a series of grooves 148, which run in the longitudinal direction of the crystallizer 126, i.e. parallel to the casting direction, and which are closed by covers 149 to define cooling channels. The cooling channels are open at both ends, forming a zone at the inlet 148a and at the outlet 148b of the channels, respectively. Arrows 150 indicate the direction of the cooling water (which is at a temperature T IN ) into the crystallizer 126. The water passes through the channels 148 along the crystallizer 126, cooling the cast product (not shown) inside the crystallizer, where it is warmed by heat exchange, and then exits the channels (arrow 152). In the figure, various configurations are inserted for the temperature sensors: optical fibers 154 with various measurement points 156; a single point sensor 158 at the outlet of the channels, inserted in a peripheral groove with an associated measurement point 162, positioned in contact with the outlet of the channel at the front of each channel, and a circular or circumferential optical fiber 160. The temperature data 164 (T OUT and / or TN ) is sent to the automation unit 166, which calculates the temperature difference ΔT at various temperature values ​​T OUT and / or T N Calculate between, and optionally T IN From these results, the automation unit processes instructions for adjusting 168 the casting parameters of the continuous casting unit 110.

[0090] FIG. 2 corresponds in essential parts to FIG. 1. A crystallizer 26 can be seen, into which liquid metal 20 is pumped through a nozzle 22. The crystallizer 26 serves to produce a flat product and is made of a long wall 25 and a narrow wall 27. Vertical through-channels 48 are made in the walls 25, 27, at least one of which illustratively contains an optical fiber 54 with a number of measurement points 56. A vertical through-channel 61 can also be seen, along with the vertical channel 48, which is provided with an optical fiber 60 with illustrative measurement point 62. These channels are crossed by a flow of cooling fluid (50, 52). The temperature data obtained from the sensors 54, 60 are transmitted 64 to an automation unit 66, which calculates the value ΔT and commands the adjustment 68 of the casting parameters of the continuous casting unit 10 equipped with the crystallizer 26.

[0091] 3 and 4 show an embodiment of a crystallization unit according to the invention, with the ingot mold 227, the crystallizer 226, and the cover 272 with the temperature sensor in a horizontal position, respectively, without the cover attached (FIG. 3) and with the cover attached (FIG. 4). The crystallization unit can be seen in a bottom view, consisting of the ingot mold 227 into which the actual crystallizer 226 is inserted, in which the outlet zone 248b of the channel can be seen. To close the space 271 between the crystallizer 226 and the ingot mold 227, a cover 272 with a series of grooves 247 is provided. These grooves 247 continue with the groove ends 248b in the crystallizer 226. An annular cavity 261 surrounds the opening 273 in the cover 272, which is complementary to the outlet of the crystallizer 226. The annular cavity 261 connects all the grooves 247 arranged transversely, i.e. horizontally, to the longitudinal extension of the crystallizer 226 .

[0092] FIG. 5 shows an enlarged view of the cover of FIGS. 3 and 4, without adding anything other than the presence of an optical fiber 260 inserted in an annular cavity 261.

[0093] It should be understood that the system for analyzing the cooling fluid temperature using optical fibers shown in Figures 3 to 5 for a long product crystallizer can of course also be applied to a crystallizer for flat products, such as a flat crystallizer for slabs, in accordance with the principles described herein, i.e., by utilizing a cover associated with the cooling channel.

[0094] FIG. 6 shows the trend of the value ΔT as a function of time under various embodiments, where ΔT is the T value for various channels. OUT It should be understood that the difference between the absolute values ​​of T and T is the result of a statistical calculation for all the individual channels measured in the crystallizer according to the invention. The graph of FIG. 6 shows the difference between the absolute values ​​of T and T as a function of time. OUT The absolute value of the temperature difference (°C) between various values ​​of ΔT AV is the average value, and ΔT MED is the median, and ΔT MAX is the maximum value, ΔTMIN is the minimum value, and ΔT TOT indicates the overall value of the main cooling. OUT By measuring only the maximum differential ΔT and using various statistical calculations and comparing the statistical values, it is possible to identify any faults in the crystallizer. By monitoring the cooling fluid temperature in some, or preferably all, of the crystallizer's outlet channels, it is possible to see if there are any abnormal temperature trends and even identify the location of the fault (in each channel). By then comparing these to the inlet temperatures, it is also possible to determine how much temperature has been removed over time. Maximum differential ΔT MAX The time trend of the average ΔT AV 1°C higher than the wall temperature, which indicates a temperature peak (indicated by an arrow) that may be an indication of a temporary reduction in heat exchange (e.g., due to a momentary peeling of the skin from the wall).

[0095] By noting this, the operator or algorithm can choose to adapt the casting parameters to resolve the emergency. In this case, the casting speed is clearly increased due to the temperature peak, along with the decrease in the temperature difference. The heat exchange is therefore more uniform throughout the channel; therefore, the skin is thinner, which is desirable, thereby exchanging heat more uniformly and adhering better to the wall. However, the increase in casting speed will probably also cause temporary peeling of the skin.

[0096] Figure 7 shows the temperature trend of a crystallizer with vertical optical fibers. It shows a vertical cross section detail in the direction of the casting trend. As can be seen from the example of the temperature distribution in the crystallizer (simulation), by measuring the temperature with different fibers passing through the cooling channels in the crystallizer wall 340, it is possible to compare the temperature distribution along the crystallizer wall 340 as the solidification progresses. By comparing the readings of several channels, it is possible to determine if there are hot or cold spots and to intervene. The entry or inlet temperature TIN The temperature drop (dark band at the top) is the same for all channels. The temperature drop starts from the meniscus zone m (light band) at a warm temperature T1 as solidification progresses, and continues at T2 and T N-1 , T N Through the temperature T at the outlet of each channel OUT The downward movement (T↓) is visible from above. N The number N=1 corresponds to a channel with a longitudinal course up to the height closest to the entrance of the crystallizer, while larger values ​​represent successive temperature detection points closer to the exit of the crystallizer. Crystallizers with rectangular angles (left diagram (a)) exhibit different cooling behavior than obtuse angles (right diagram (b)). The "nose" of the band corresponds to a zone that does not coincide with a cooling channel (not shown, but present in wall 340) and cools with a slight delay compared to the zone immediately behind the cooling channel.

[0097] 8 shows an exemplary embodiment of the positioning and fixation of an optical fiber with a plurality of measurement points 362 at the end of the crystallizer 326. A series of cooling channels 348 impinge on the optical fiber 360 arranged along the periphery of the crystallizer 326 in their exit zone. One possibility for fixing the optical fiber 360 is to apply the respective hooks 380 directly to the crystallizer 326. An alternative preferred fixation instead provides for maintaining the fiber 360 in an enclosed position between a pair of covers 372a and 372b, identified by the respective grooves 361.

Claims

1. A device for controlling heat exchange in a crystallizer (26, 126, 226, 326), comprising: (a) a crystallization unit comprising: (a-1) A crystallizer (26, 126, 226, 326) for continuous casting, (a-1.1) a tubular body with at least one wall (25, 27, 340) defining a longitudinal casting cavity therethrough; (a-1.2) a plurality of first cooling channels (48, 148, 348), preferably longitudinal, with one end serving as an inlet (148a) and the other end serving as an outlet (148b, 248b); a crystallization unit comprising a crystallizer (26, 126, 226, 326) having a (b) one or more first temperature sensors (54, 60, 154, 158, 160, 260, 360, 362); a temperature T at the associated outlet of a cooling fluid located at the outlet (148b, 248b) of the first cooling channel (48, 148, 348) and flowing through the first cooling channel (48, 148, 348) during use of the crystallizer (26, 126, 226, 326); ＯＵＴ Measure and / or One or more respective temperatures T are positioned inside the first cooling channel (48, 148, 348) along its longitudinal extension, preferably at N different heights, corresponding to different heights of the cooling fluid flowing (50, 52, 150, 152) through the first channel (48, 148, 348) during use of the crystallizer (26, 126, 226, 326). Ｎ To measure one or more first temperature sensors (54, 60, 154, 158, 160, 260, 360, 362); Equipped with if there is only one temperature sensor, said only one temperature sensor is a multi-point (54, 56, 154, 160, 260, 360) sensor (56, 62, 156, 162, 362), preferably a Bragg grating optical fiber; A device for controlling heat exchange in a crystallizer (26, 126, 226, 326).

2. (c) the inlet temperature T of a cooling fluid located upstream (148a, 248a) of the first cooling channel (48, 148, 348) and flowing through (50, 52, 150, 152) the first cooling channel (48, 148, 348) during use of the crystallizer (26, 126, 226, 326). ＩＮ at least one second temperature sensor that measures 2. The device for controlling heat exchange in a crystallizer (26, 126, 226, 326) according to claim 1, further comprising:

3. 3. The device for controlling heat exchange in a crystallizer (26, 126, 226, 326) according to claim 1 or 2, characterized in that the crystallization unit further comprises a cooling fluid source, in particular a cooling system or circuit connected to the first cooling channel (48, 148, 348) and supplying cooling fluid through its inlets (148a, 248a).

4. (d) a control unit (66, 166) comprising: (d-1) the outlet temperature T of each of the cooling channels (48, 148, 348) ＯＵＴ and / or receive measurement signals of temperatures T at various heights of the crystallizer (26, 126, 226, 326) from the first sensor (54, 60, 154, 158, 160, 260, 360, 362). Ｎ to receive the measurement signal (d-2) Optionally, if at least one second temperature sensor is present, a temperature T ＩＮ to receive the measurement signal (d-3) calculate the temperature difference ΔT among the received temperature values; and (d-4) processing commands for controlling the casting parameters (68, 168) of the continuous casting plant (10, 110) equipped with said crystallizer (26, 126, 226, 326) based on the calculated value ΔT; The heat exchange control device according to any one of claims 1 to 3, further comprising a control unit (66, 166) configured to:

5. A heat exchange control device according to any one of claims 1 to 4, characterized in that the first temperature sensor is a multi-point (56, 62, 156, 162, 362) sensor (54, 56, 154, 160, 260, 360), preferably a Bragg grating optical fiber.

6. 6. The heat exchange control device according to claim 1, further comprising a plurality of first single-point sensors or at least one first multi-point sensor positioned circumferentially around an end of the crystallizer and positioned at the outlet of the first cooling channel, whereby the sensor is affected by the flow of cooling fluid at the outlet from the first cooling channel.

7. 7. The heat exchange control device according to claim 6, wherein the crystallizer (26, 126, 326) further comprises a surrounding cavity (61, 361) at the end, i.e., in the outlet zone (148b, 248b) of the first cooling channel (48, 148, 348), for accommodating a plurality of the single-point sensors or at least one of the multi-point (62, 162, 262) sensors (60, 160, 260).

8. 8. A heat exchange control device as described in claim 6 or 7, characterized in that the plurality of single-point sensors or the plurality of multi-point (60, 160, 260) sensors (62, 162, 262) are positioned directly at the physical outlet of each of the cooling channels or positioned outside at the end of each of the cooling channels, the distance of the temperature measurement sensors to the physical outlet being preferably less than 10 cm, more preferably less than 4 cm, and even more preferably less than 2 cm.

9. The crystallization unit comprises: (a-2) an ingot mold (227) into which the crystallizer (226, 326) is inserted; (a-3) the first cover (272, 372a), preferably disk-shaped and adapted to close the gap (271) between the crystallizer (226, 326) and the ingot mold (227), the opening (273) being complementary to the outlet of the crystallizer (226, 326); (a-3.1) a plurality of second channels (247) arranged radially around the opening (273) and continuous with the first cooling channel (248b) when the gap (271) is in a closed state using the first cover (272, 372a); (a-3.2) a cavity, preferably annular (261, 361), extending around said central opening (273), communicating with said second channel (247) and housing one or more said first temperature sensors (260, 360, 362), in particular multi-point sensors; a first cover (272, 372a) having The heat exchange control device according to claim 7 or 8, further comprising:

10. the first cover (272, 372a) further comprises a plurality of second channels in the form of grooves (247) and a cavity (261, 361), preferably annular and in the form of a groove as defined in claim 9, and the crystallization unit comprises: (a-4) A second cover (372b), (a-4.1) having a central opening, preferably disk-shaped, adapted to close the gap between the crystallizer and the ingot mold, said opening being complementary to the outlet of the crystallizer (326); (a-4.2) being compatible with the first cover (272, 372a) so as to surround the one or more temperature sensors (260, 360, 362) and close the second groove (247) between the first (272, 372a) and second cover (372b); The heat exchange control device of claim 9, further comprising a second cover (372b).

11. A heat exchange control device according to any one of claims 1 to 10, characterized in that a multi-point (56, 156) temperature sensor (54, 154) is inserted in at least one of the cooling channels (48, 148, 348), preferably longitudinally and therefore parallel to the casting direction.

12. A cover (272, 372a, 372b) for closing a gap (271) between an ingot mold (227) and a crystallizer (226, 326) inserted therein, the cover (272, 372a, 372b) preferably being disk-shaped and having a central opening (273), the opening (273) being complementary to the outlet of the crystallizer (226, 326), the cover (272, 372a, 372b) comprising: (i) a plurality of channels (247) radially arranged around the opening (273), the covers (272, 372a, 372b) aligned with cooling channels (148b, 248b, 348) present in the crystallizer (226, 326) when the gap (271) is in a closed state with the covers (272, 372a, 372b); and (ii) a cavity, preferably annular (261, 361), extending around said central opening (273) and preferably connected to said radial channel (247), adapted to accommodate one or more temperature sensors (260, 360, 362), in particular multi-point sensors, in particular Bragg grating optical fibers, and optionally (iii) one or more temperature sensors (260, 360, 362), in particular multipoint sensors, in particular Bragg grating optical fibers, inserted into said cavity (261, 361); A cover (272, 372a, 372b) comprising:

13. 1. A method for controlling heat exchange in a crystallizer (26, 126, 226, 326), comprising: (I) providing said crystallizer (26, 126, 226, 326) with preferably longitudinal cooling channels applied to at least one wall (25, 27, 340) of said crystallizer (26, 126, 226, 326), (II) introducing a cooling fluid into said cooling channels (48, 148, 348) such that the flow of the cooling fluid is preferably parallel to the casting direction, said cooling fluid preferably having a common inlet temperature T ＩＮ and performing casting through said crystallizer (26, 126, 226, 326); (III) the temperature of the cooling fluid at the outlet (148b, 248b) (T ＯＵＴ ) for a plurality of said cooling channels (48, 148, 348); and / or measuring the temperature (T) of the cooling fluid along said cooling channel (48, 148, 348) for at least one, but preferably a plurality, of said cooling channels (48, 148, 348). Ｎ ) measuring the (IV) the temperature T at the inlet to the cooling channel (48, 148, 348) ＩＮ optionally measuring or determining (V) Preferably, for all channels (48, 148, 348) provided with temperature sensors (54, 56, 154, 158, 160, 260, 360, 362), calculating a temperature difference ΔT, wherein said temperature difference ΔT is (V-1) At least two outlet temperatures T in two different cooling channels (48, 148, 348) ＯＵＴ The one between (V-2) between two temperatures measured at different heights of the cooling channel (48, 148, 348) or between two temperatures measured at the same height but in different cooling channels (48, 148, 348); and optionally, (V-3) Inlet temperature T of the cooling channel (48, 148, 348) ＩＮ and outlet temperature T ＯＵＴ and / or (V-4) Inlet temperature T ＩＮ and the temperature T along the cooling channel (48, 148, 348). Ｎ Between a step of calculating (VI) identifying irregularities in the value ΔT; and (VII) correcting casting parameters, such as casting speed or oiling, based on the irregularities determined in step (VI); A method comprising:

14. Use of a device for controlling heat exchange in a crystallizer (26, 126, 226, 326) according to any one of claims 9 to 11 in a continuous casting process with measurement of heat exchange in the crystallizer (26, 126, 226, 326), comprising: (α) the worn crystallizer (26, 126, 226, 326) is replaced with a new crystallizer, or (β) the crystallizer (26, 126, 226, 326) is replaced with a crystallizer having a different shape and / or other dimensions, so that the first cover (272, 372a, 372b) is replaced with a new cover whose shape and / or dimensions are adapted to the new crystallizer and to the respective gap created between the new crystallizer and the ingot mold (227); Use of the device.

15. A cover kit comprising: (i) a plurality of covers (272, 372a, 372b) according to claim 12, which are compatible between the crystallizer (26, 126, 226, 326) and the ingot mold (227) to close the gap (271) therebetween and enclose the temperature sensor (260, 360, 362) therebetween; (ii) a plurality of covers (272, 372a, 372b) according to claim 12, each having a different shape and / or size and adapted to various types of crystallizers (26, 126, 226, 326); A cover kit comprising:

16. A continuous casting plant comprising a heat exchange control device according to any one of claims 1 to 11.

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