HEAT EXCHANGE APPARATUS

Description

HEAT EXCHANGE APPARATUS ************ Field of invention The present invention relates to a heat exchange apparatus for exchange heat with a moving metal strip, such as steel along a plant, in particular an annealing plant such as a annealing and galvanizing line, known in English as “Hot-dip galvanizing line” (HDGL), or a continuous annealing line, known in English as “continuous annealing line” (CAL). State of the art In the galvanizing lines, the strip is annealed in special ovens before being galvanized and / or painted. In fact, since during cold rolling the strip becomes hard and brittle, annealing is done to reduce the hardness and improve the formability of the material. Additionally, annealing helps to eliminate any surface defects present in the tape, ensuring a more uniform and better quality surface before galvanizing. During this process the strip is heated in annealing furnaces, which They generally use fossil fuels and more recently have started to use, in partial or total substitution of fossil fuels, furnaces induction and / or with electric heating elements. This operation however involves bringing the tape from a temperature essentially ambient at around 950-1000°C, with the consequent consumption energetic. The annealing process, at its end, releases a hot ribbon ready to be galvanized, but for galvanizing it is sufficient to have a strip temperature of approximately 500°C. Therefore, a lot of heat energy is imparted to the tape during the process of annealing is subsequently lost. Further heat energy is lost downstream of galvanizing when the strip, a once it has passed through the liquid zinc tank, it passes through the air blades and the cooling zone, which causes the zinc coating to solidify. There is therefore a need to reduce energy consumption related to heating the tape inside the annealing furnaces, particularly in the initial preheating stages which bring the material from room temperature to the target temperature. It is also necessary to cool the strip downstream of the annealing treatment there is also a need to recover at least part of this heat for place it back on the heating belt. There is therefore a need to create an innovative exchange apparatus thermal that allows us to respond to these needs, obtaining the consequent advantages in terms of reduction of energy consumption and therefore impact environmental equivalent. Summary of the invention The purpose of the present invention is to create a heat exchange apparatus equipped with at least one bridle roller capable of achieving optimal heat exchange between the conveyor belt and the said bridle roller, in particular to operate a controlled cooling, or controlled preheating, of the tape that is partially wraps around said at least one roller. Another object of the present invention is to provide an exchange apparatus thermal in which said at least one bridle roller has a simple design and low weight, while maintaining a high stability considering the stresses to which it is subjected in following contact with the tensioned tape and the passage of a fluid heat transfer medium inside it, which can reach high temperatures with the risk to cause part of the roller structure to deform. A further object of the present invention is to provide an exchange apparatus thermal that can be positioned close to, upstream and / or downstream of, an annealing plant, or incorporated into said annealing apparatus, in order to recover at least partially the thermal energy that is removed from the annealed metal strip in a controlled cooling phase and reuse it by transferring this energy recovered from the metal strip entering the annealing apparatus by means of a heat transfer fluid, such as diathermic oil, thus obtaining a preheating of the product to be reheated with obvious advantages for the environment and the reduction of furnace operating costs. The present invention, therefore, aims to achieve the above purposes. discussed by realizing a heat exchange apparatus comprising at least one bridle roller to exchange heat with a metal belt advancing along a system, said at least one bridle roller comprising - a hollow cylindrical body defining a longitudinal axis of rotation X; - an external shell fixed on the external lateral surface of said cylindrical body hollow and defining an external cylindrical radial surface of said roller, coaxial to said X-axis, for a partial winding of the metal strip around said outer shell during its advancement; - at least one internal channel, created by the coupling between the lateral surface external surface of said hollow cylindrical body and an internal cylindrical radial surface of the outer shell; wherein at least a lateral end portion of said hollow cylindrical body comprises a respective annular cavity suitable for containing a fluid heat transfer medium and to distribute it in said at least one internal channel; in which a hollow transmission element is provided, with which at least one lateral end portion is connected to receive the transmission of a motion of rotation around said longitudinal axis X, said hollow transmission element comprising an internal conduit for supplying said heat transfer fluid into said annular gap. A further aspect of the invention relates to an annealing plant for a strip metal moving along one direction, said system comprising in succession - at least one preheating section; - at least one heating section; - at least one temperature maintenance section; - at least one cooling section; in which a first heat exchange apparatus is provided as described above in said at least one preheating section; in which a second heat exchange apparatus is provided as described above in said at least one cooling section; and in which a closed circuit of heat transfer fluid is provided, configured for pass through the said second heat exchange apparatus to remove energy thermal transfer from the metal tape by conduction, obtaining a high-temperature heat transfer fluid temperature, let it be said first heat exchange apparatus to release energy thermal transfer to the metal tape by conduction, obtaining low temperature heat transfer fluid temperature. The dependent claims describe preferred embodiments. of the invention. Brief description of the figures Further features and advantages of the invention will become more apparent. evident in light of the detailed description of preferred embodiments, but not exclusive, of the solution of the invention illustrated by way of example and not limited to, with the aid of the attached drawing tables in which: Figure 1 represents a perspective view of a bridle roller of the apparatus according to the invention; Figure 2 represents a side view of two bridle rollers of the apparatus according to the invention; Figure 3 represents a side sectional view of a first form of making the bridle roller; Figure 4 represents a first perspective view of part of the bridle roller of Figure 3; Figure 5 represents a side sectional view of a second form of making the bridle roller; Figure 6 represents a first perspective view of part of the bridle roller of Figure 5; Figure 7 represents a second perspective view of part of the bridle roller of Figure 3; Figure 8 represents a second perspective view of part of the bridle roller of Figure 5; Figure 9 represents a partially sectioned side view of some components of the bridle roller according to the invention; Figure 9a represents a partially sectioned side view of said bridle roller components in an alternative variant thereof; Figure 10 represents a perspective view of a first component of the roller bridle according to the invention; Figure 11 represents a perspective view of a second component of the bridle roller according to the invention; Figure 12 represents a perspective view of a detail of Figure 9; Figure 13 represents a schematic of an annealing apparatus comprising bridle rollers according to the invention; Figure 14 represents a perspective view of a preferred configuration of an apparatus according to the invention. The same reference numbers in the figures identify the same elements or components. Detailed description of preferred embodiments of the invention With reference to Figures 1-12, some embodiments are shown. examples of a bridle roller of the heat exchange apparatus according to the invention, specially designed to exchange heat with a ribbon metal advancing along a plant. In general, bridle rollers are rollers used to modify the tension of the belt in belt conveyor systems. rolling for flat metal products, thanks to the well-known change of direction that they exert on the metal strip, for example defining a winding path of the tape, tying it to control its tension. The heat exchange apparatus of the present invention reuses this technology, applying it in a cold rolling mill for flat products, preferably in the plant area upstream of galvanizing in an annealing line and galvanizing, known in English as “Hot-dip galvanizing line” (HDGL), or in a continuous annealing line (CAL), in order to achieve optimal heat exchange between the conveyor belt and the bridle rollers, in particular to carry out controlled cooling or preheating controlled, of the tape that partially wraps around said bridle rollers. As is known, metal tape is a product having a dimension, that is, the thickness, considerably smaller than the other two dimensions, i.e. length and width length. In all embodiments of the invention, the heat exchange apparatus comprises at least one bridle roller for exchanging heat with a metal strip in advancement along a system. Said at least one bridle roller comprises (Figure 1 and 3-8): - a hollow cylindrical body 1 defining a longitudinal axis of rotation X; - an outer shell 2 fixed on the external lateral surface of the cylindrical body cable 1 and defining an external cylindrical radial surface of the roller or surface external side of the roller, coaxial to the said X axis, for partial winding of the metal tape around the outer shell 2 as it advances; - at least one internal channel 3, created by the coupling between the surface external side of the hollow cylindrical body 1 and a cylindrical radial surface internal, or inner lateral surface, of the outer shell 2. Advantageously, at least one lateral end portion 5 of the body hollow cylindrical 1 includes within it a respective annular cavity 6 suitable for receiving a heat transfer fluid and distributing it in at least one internal channel 3. A hollow transmission element 7 is arranged along the longitudinal axis X and rigidly connected, for example by keying, to said at least one lateral end portion 5 for transmitting a rotational motion to the roller bridle around the X-axis. Said hollow transmission element 7 comprises a internal duct 8 to feed the heat transfer fluid into said cavity ring finger 6. The configuration just described allows for an optimal exchange thermal between the conveyor belt in transit, which partially wraps around the bridle roller, and heat transfer fluid that flows through at least one internal peripheral channel 3 of the roller bridle. In a preferred variant, the seal between the cylindrical body 1 and the outer shell 2 is made by external lateral welding along one direction circumferential, avoiding the use of very expensive o-rings suitable for sealing the heat transfer fluid. This external lateral welding is foreseen, for example, in corresponding to a circumferential area 90, indicated in Figure 6. Preferably, the annular gap 6 is delimited along a radial direction from an external lateral surface, preferably cylindrical, of said element transmission cable 7 and an internal annular end surface of the body hollow cylindrical 1. The annular cavity 6 is also preferably delimited, along a direction parallel to the X-axis, from at least two parallel walls, to example only two parallel walls, orthogonal to the longitudinal axis X. In a preferred variant of the invention, in said at least one bridle roller are expected: - a plurality of first radial holes 9, made in the thickness of the hollow element of transmission 7, and which connect the internal duct 8 with the annular cavity 6; - and a plurality of second radial holes 10, made in the thickness of a part radially peripheral of said at least one lateral end portion 5, and that connect the annular gap 6 to said at least one internal channel 3. Preferably, said at least one internal channel 3 comprises two or three channels helical, preferably connected in parallel, delimited by a respective helical groove 4, made on the external lateral surface of the body hollow cylindrical 1, and from the cylindrical internal radial surface of the outer shell 2. The possibility of providing only one internal helical channel 3, or more, is not excluded of three internal helical channels. In a first variant of the bridle roller, illustrated in Figures 3-4 and 7, said at least a lateral end portion 5 has a plurality of through holes 11 defining a respective axis parallel to the longitudinal axis X, and preferably arranged along a circumference coaxial to the said longitudinal axis X, so that the volume of the respective annular cavity 6 inside the portion of lateral end 5 is reduced. Preferably, the number of said through holes 11 varies from three to nine. In the example in Figure 7, six through holes 11, identical to each other, are foreseen in the lateral end portion 5. Preferably the distance between the two parallel walls that delimit the cavity ring 6 is included in a range from 50 to 350 mm, for example from 100 to 350 mm. In a second variant of the bridle roller, illustrated in Figures 5-6 and 8, they are instead expected: - radial reinforcement elements 12, preferably angularly equidistant from each other on the other, arranged between the two parallel walls so as to divide the cavity annular 6 in a plurality of sectors 60, preferably corresponding to sectors circular shapes that are equal to each other; - at least one first radial hole 9, for example a single radial hole 9, which connects the internal duct 8 with a respective sector 60, and at least one second radial hole 10 which connects said respective sector 60 to at least one internal channel 3. Preferably, the number of radial reinforcing elements 12, e.g. bars radial, and therefore the number of sectors 60 varies from four to eight. In the example Figure 8 features six radial reinforcement elements 12, and therefore six sectors 60, equal to each other, in the lateral end portion 5. Preferably the distance between the two parallel walls that delimit the cavity ring 6 is included in a range from 40 to 100 mm, for example from 40 to 90 mm. With both variants of the bridle roller, described above, the simple design and the reduced weight of the bridle roller, almost completely empty inside, allows however, to maintain a high stability of the roller, considering the stresses at to which it is subjected following contact with the tensioned tape and when a heat transfer fluid passes through it, which can reach high temperatures with the risk of bringing part of the roller structure to to deform. In particular, the first variant of the bridle roller allows for high stability structural due to the presence of through holes 11 which determine corresponding tubular reinforcement elements inside the annular cavity 6 and a resulting in a reduced volume for the heat transfer fluid in transit in the cavity annular. This configuration also allows the use of a hollow element of transmission a simple first lateral hub 7. A second lateral hub 7' it can be foreseen in correspondence with a second end portion lateral 5' of the hollow cylindrical body 1, opposite the lateral end portion 5 (Figure 3). Instead, the second variant of the bridle roller allows for high stability structural despite a greater simplicity in the construction of the portions of lateral ends 5, 5', especially if it were used as a transmission element used a thru axle hub 7, at least partially hollow, which passes through the roller along the longitudinal axis X and on which both portions are connected of lateral ends 5, 5' (Figure 5). In a first embodiment of the heat exchange apparatus of the invention, partially illustrated in Figures 3, 5 and 9, the heat transfer fluid enters the bridle roller at a first portion of the lateral end 5 and comes out of the bridle roller at a second portion of lateral end 5', opposite the first portion of lateral end 5. Both lateral end portions 5, 5' of the hollow cylindrical body 1 include a respective annular gap 6, 6'. A first annular gap 6 of the first lateral end portion 5 is suitable for receiving the heat transfer fluid from the internal duct 8 of a first hub lateral 7, or of a hub with a through axle, and to distribute it in said at least an internal channel 3. In particular, first radial holes 9 connect the internal duct 8 to the first annular gap 6, and second radial holes 10 connect said first annular gap 6 to at least one internal channel 3. A second annular gap 6' of the second lateral end portion 5' is, instead, suitable for receiving the heat transfer fluid from said at least one channel internal 3 and convey it into a further internal duct 8' of a second hub lateral 7', or of said through-axle hub, on which said second portion of lateral end 5'. In particular, third radial holes 10' connect said at least one internal channel 3 to the second interspace 6', and fourth radial holes 9' connect said second 6' interspace to the additional internal duct 8'. First annular gap 6 and second annular gap 6' are each delimited by two respective parallel walls, orthogonal to the longitudinal axis X. In the case of the first variant of the bridle roller (Figures 3-4 and 7), both portions of lateral ends 5, 5' have a respective plurality of through holes 11 defining a respective axis parallel to the longitudinal axis X, and preferably arranged along a circumference coaxial to the said longitudinal axis X, so that the volume of the respective annular space 6, 6' is reduced. Preferably, both lateral end portions 5, 5' are provided with a respective external cover panel 20. Said external cover panels 20 are held integral with the respective end portion 5, 5' and held integral with each other by means of a plurality of tie rods 21, each tie rod 21 passing through a respective through hole 11 of each end portion 5, 5'. Each cover panel 20, of substantially circular shape, can be formed from a single piece or from at least two or three pieces, for example three pieces that each define a central angle of 120°. In the case of the second variant of the bridle roller (Figures 5-6 and 8), both lateral end portions 5, 5' have respective radial reinforcement elements 12 between the two parallel walls such as to divide, respectively, the first annular gap 6 in a plurality of first sectors 60 and the second 6' annular gap in a plurality of second sectors. The following are also provided: - at least a first radial hole 9 which connects the internal duct 8 with a respective first sector 60; - at least one second radial hole 10 connecting said respective first sector to at least one internal channel 3; - at least a third radial hole connecting said at least one internal channel 3 to a respective second sector; - and at least a fourth radial hole connecting said respective second sector to the additional internal duct 8'. Preferably, both lateral end portions 5, 5' are provided with a respective external cover panel 20. In a preferred variant of the heat exchange apparatus of the invention, upstream of at least one bridle roller are provided: - a fixed pipe 24 for the passage of heat transfer fluid; - a hollow transmission shaft 15 provided with an integral tube 16 inside it to it and coaxial to the longitudinal axis X, and solidly connected to the first lateral hub 7, or to the through-axle hub, so that tube 16 and internal duct 8 of the lateral hub 7 define a rotating pipe 16, 8; - a rotary joint 18 connecting the fixed pipe 24 to said rotating pipe 16, 8. Preferably, the rotary joint 18 comprises a fixed part 25, connected to the fixed pipe 24, and a rotating conduit 17 inside said fixed part 25 communicating with the rotating pipe 16, 8. In a preferred variant, the rotary joint 18 further comprises a flange with conical coupling 26 arranged on the rotating duct 17 and fixed to the shaft transmission cable 15, for example by means of screws arranged along the periphery of the flange and inserted into corresponding peripheral holes of the hollow transmission shaft 15. In this way the integral rotation of the rotating duct 17 is ensured and rotating pipe 16, 8. Hydraulic sealing elements can be provided in correspondence with the connection between said rotating conduit 17 and said rotating pipe 16, 8, and also between pipe 16 and internal duct 8. Preferably, upstream of the at least one bridle roller the following are further provided: - at least one support 19 of the hollow transmission shaft 15, with bearings interposed between said support 19 and said hollow transmission shaft 15; - and a plurality of cooling fins 22, protruding from the hollow shaft of transmission 15, and arranged between said at least one support 19 and a first end of the hollow drive shaft 15 connected to the first lateral hub 7 or thru-axle hub. Because heat is transmitted outwards by the heat transfer fluid, which flows inside the side hub 7, or thru axle hub, and other heat can also be generated during rotation in the coupling zone between hollow drive shaft 15 and said hub, these cooling fins 22 They allow heat to be dissipated, preventing the bearings from overheating. The connection between the hollow drive shaft 15 and the hub 7 can be made, as illustrated in Figures 9-11, by means of a flanged coupling. The rotary hydraulic joint 18, as illustrated in Figure 9, is therefore connected to package with hub 7. Furthermore, it is preferable to also provide an obstacle connection between the hollow shaft of transmission 15 and hub 7, for example via tongue, spline profiles or longitudinal spines. In Figures 10-11, for example, the quarry 23, 23' is visible, partly made on the hub 7 and partly inside the drive shaft 15, where it is inserted a tab (not shown). The tab makes the connection by transmitting the stress on the side walls of the slot, while radially there is a play; therefore, It acts as an obstacle, preventing the relative rotational motion. In a further preferred variant, the tube 16 is provided in its thickness with a 16' annular inner tube, coaxial to the X-axis, to reduce the transmission of heat from the heat transfer fluid to the outside, and in particular towards the aforementioned bearings. The hollow drive shaft 15 may be driven by a motor 13, arranged along an axis parallel to, and distinct from, the longitudinal axis X. Preferably, a 14 chain drive is provided, optionally with epicyclic reducer, connecting the motor 13 to one end of the hollow shaft of transmission 15 connected to rotary joint 18. In a preferred variant, a regulation system is provided to adjust the tension of the chain of said chain drive 14, e.g. an actuator mechanical or pneumatic or hydraulic. Figures 1-2 illustrate, for example, a mechanical actuator 81 including a screw adjustment system. In a second embodiment of the heat exchange apparatus of the invention, partially illustrated in Figure 9a, instead, the fluid heat transfer medium enters and exits the bridle roller from the same side, i.e. in correspondence of the first portion of the lateral end 5. The annular gap 6 is divided into two adjacent and parallel portions 91, 93, separated by an intermediate wall 92, preferably parallel to the two walls parallels indicated above. The hollow transmission element 7, in the form of a lateral hub or a hub with through shaft, includes an internal conduit 8 to feed the fluid heat transfer medium, entering the roller, in a first portion 91 of said cavity ring finger 6. A first series of first radial holes 9 connects the internal duct 8 to said first portion 91 of the annular gap 6. A first series of second radial holes 10 connects the first portion 91 of the annular gap 6 to an inlet section of the at least one channel interior 3. Said at least one internal channel 3 is configured to allow the fluid heat transfer medium to reach the second portion of the 5' side end and return back towards the first portion of lateral end 5. A second set of second radial holes 10 then connects an outlet section of the at least one internal channel 3 with the second portion 93 of the cavity ring finger 6. A second series of first radial holes 9 finally connects said second portion 93 of the annular cavity 6 to a further internal duct 80 of the hollow element of transmission 7. Preferably, the further internal duct 80 is arranged coaxially to, and inside of, said internal duct 8. The further internal duct 80 has a suitable extension that passes through both the tube 16 that the rotating conduit 17 of the rotating joint 18. According to a further aspect of the invention, a system of annealing for a metal strip advancing along one direction, comprising at least two heat exchange devices, like the one above described. In particular, this annealing plant comprises in succession (Figure 13): - at least one preheating section 30; - at least one heating section 31; - at least one temperature maintenance section 32; - at least one cooling section 33. Advantageously, a first heat exchange apparatus is provided in said at least one preheating section 30; a second heat exchange apparatus in said at least one cooling section 33; and a closed fluid circuit heat transfer medium configured to pass through both the second exchange apparatus thermal to remove heat energy from the metal strip by conduction, obtaining high temperature heat transfer fluid, both the first exchange apparatus thermal to release thermal energy to the metal strip by conduction obtaining low-temperature heat transfer fluid. It is preferable to provide only one preheating section 30, only one section of heating 31, a single temperature maintenance section 32, and a single cooling section 33. Therefore, in steady state operation, the heat transfer fluid allows for recover completely or partially the thermal energy that is removed from the annealed metal strip in the cooling section 33 and reuse it transferring it to the metal belt in the preheating section 30, at the entrance to the plant, thus obtaining a preheating of the product to be re-baked with evident environmental benefits and reduction of operating costs of the heating section 30. Preferably, the first heat exchange apparatus comprises a plurality of 34 heating bridle rollers for the advancement of the metal strip; the second heat exchange apparatus comprises a plurality of bridle rollers of cooling 35 for the advancement of the metal strip; and the closed circuit of heat transfer fluid passes in series through both the cooling bridle rollers 35, provided in the cooling section 33, both the heating bridle rollers 34 provided in the preheating section 30. The bridle rollers 34, 35 are like the bridle roller above described in one of its variants. As illustrated in Figure 14, a preferred configuration of each apparatus of heat exchange provides that the heating bridle rollers 34 and the bridle rollers of cooling 35 are arranged so that each bridle roller is wrapped from the metal tape for at least 190°. Preferably, both heat exchangers are provided with a even number, preferably six, of bridle rollers 34, 35 which are arranged in succession between them, in groups of two bridle rollers at different heights from each other, preferably just two different heights. As illustrated in Figures 2 and 14, considering each group of two rollers bridle, a preferred variant provides that the height difference between the two rollers bridle, equal to each other, is determined by the different height of the respective frame of support 82. Thanks to the chain tension adjustment system of the chain transmission 14 it is possible to position the motors 13 substantially at the same height on the respective support frames 82, while the length of the chain for the highest bridle roller is greater than the length of the roller chain lower bridle. With this configuration, the weight of the supporting carpentry is significantly reduced. The support frames 82 can be connected by two parallel beams 94, each beam 94 at a respective lateral end of the rollers bridle of the heat exchange apparatus. Referring to Figure 13, preferably along the circuit, considering a direction of flow of the heat transfer fluid, are foreseen - a first storage and handling system 36, 37 of the heat transfer fluid at high temperature, arranged along a first section 70 of the circuit from said section of cooling 33 to said preheating section 30; - and a second fluid storage and handling system 38, 39 low temperature heat transfer medium, arranged along a second section 71 of the circuit from said preheating section 30 to said cooling section 33. In a preferred variant, the first storage and handling system 36, 37 includes a first tank 36 for the storage of the high temperature heat transfer fluid temperature and a first pumping unit 37 configured to regulate the flow rate of the heat transfer fluid towards the preheating section 30. Said first tank 36 preferably has insulated walls to minimize the energy lost in the environment. In fact, this tank 36 creates a thermal energy store (Thermal Energy Storage) where the high temperature heat transfer fluid is stored which will be used to preheat the metal strip 40 entering the furnace annealing, i.e. at the entrance to heating section 31. In essence, by decoupling the cooling section 33 from the preheating 30, in all cases where the thermal energy extracted from the belt 40 during the cooling is different from that required by the tape to be preheated in entrance to the annealing apparatus, the difference in excess or deficiency is respectively stored or extracted from tank 36. Preferably, the flow of high-temperature heat transfer fluid from the tank 36 is controlled by the pumping unit 37, in which the drive motor of the pump is variable speed to achieve a control or modification mode of the flow towards the preheating section 30 through a duct of adduction 41. The high temperature heat transfer fluid then reaches the preheating section 30 through the supply duct 41. Similarly, the second storage and handling system 38, 39 includes a second tank 38 for storing the heat transfer fluid low temperature and a second pumping unit 39 configured for regulate the flow of said heat transfer fluid towards the cooling section 33. Said second tank 19 preferably has non-insulated walls. Preferably, the flow of low-temperature heat transfer fluid from the tank 38 is controlled by the pumping unit 39 in which the drive motor of the pump is variable speed to achieve a control or modification mode of the flow towards the cooling section 33 through a duct of adduction 42. The low temperature heat transfer fluid therefore reaches the cooling section 33 through the supply duct 42. Optionally, a heating device 43 is provided downstream of the first tank 36, preferably between the first tank 36 and the first pumping unit 37, for heat the heat transfer fluid in case of cold start of the device annealing, for example after a long maintenance stop. By way of example, the heating device 43 is provided with at least one heating element, such as an armored electric resistor immersed in an internal volume of the device 43 crossed by the heat transfer fluid. In a variant of the annealing apparatus of the invention, between the section of temperature maintenance 32 and cooling section 33 is provided an additional gas jet cooling section 44 to perform a preliminary cooling of the tape. In this way the metal tape 40, after completing the cycle of recrystallization in the temperature holding section 32, enters into this 44 gas jet cooling section where it undergoes a first step of slow cooling by the effect of a cold gas, preferably distributed by upper cooling plenum 45 and lower 46. This section of cooling 44 is used in all cases where cooling is required slow from the metallurgical recipe depending on the quality of the product to be obtained. Optionally, the cooling section 44 can be equipped with additional heat recovery systems, in which the gas flows ejected from the plenums of upper cooling 45 and lower 46, once heated having removed heat from the product, are removed by means of a pumping system or compression 47 and sent to a further heat exchanger 48, which cools the hot gas arriving from an inlet pipe 49, sending it back to the plenums of cooling 45, 46, once cooled, through an outlet pipe 50. Preferably, the cooling rate in this section of cooling 44 is included in a range from 5 to 15 C° / s. The metal strip 40, after the cooling section 44, reaches a temperature from 650 to 900°C and enters the cooling section 33. In a further variant of the annealing apparatus of the invention, downstream of the cooling section 33 a post-heating section 51 is provided for heat the metal strip to a temperature lower than that of solubilization. The function of this post-heating section 51 is purely metallurgical. In fact, since the post-heating occurs at a lower temperature than that of solubilization, it allows to activate diffusive phenomena that induce stable coherent phase formation. Preferably, downstream of said post-heating section 51 a further one is provided cooling section 52 with gas jets, equal to the cooling section 44, to bring the metal strip 40 to a target temperature for output from the apparatus. In the example in Figure 13, the annealing apparatus includes of the invention both the gas jet cooling section 44 and the post heating section 51 followed by the further gas jet cooling section 52. In some variants of the device, depending on the quality of the input tape and to the metallurgical quality that is desired to be obtained, the section can be removed gas jet cooling section 44 and post-heating section 51, and possibly also the gas jet cooling section 52.

Claims

1. Heat exchange apparatus comprising at least one bridle roller for exchanging heat with a metal strip advancing along a line, said at least one bridle roller comprising - a hollow cylindrical body (1) defining a longitudinal axis of rotation (X); - an outer shell (2) fixed on the outer lateral surface of said hollow cylindrical body (1) and defining an outer cylindrical radial surface of said roller, coaxial to said axis (X), for a partial wrapping of the metal strip around said outer shell (2) during its advancement; - at least one internal channel (3), created by the coupling between the outer lateral surface of said hollow cylindrical body (1) and an internal cylindrical radial surface of the outer shell (2);wherein at least one lateral end portion (5) of said hollow cylindrical body (1) comprises a respective annular cavity (6) suitable for containing a heat-transfer fluid and distributing it in said at least one internal channel (3); wherein a hollow transmission element (7) is provided, with which said at least one lateral end portion (5) is connected to receive the transmission of a rotational motion around said longitudinal axis (X), said hollow transmission element (7) comprising an internal duct (8) for feeding said heat-transfer fluid into said annular cavity (6).; 2. Apparatus according to claim 1, wherein said at least one bridle roller includes - a plurality of first radial holes (9), made in the thickness of said hollow transmission element (7), which connect said internal duct (8) with said annular gap (6); - and a second plurality of second radial holes (10), made in the thickness of a radially peripheral part of said at least one lateral end portion (5), which connect said annular gap (6) with said at least one internal channel (3).

3. Apparatus according to claim 1 or 2, wherein the annular cavity (6) of said at least one lateral end portion (5) is delimited by at least two parallel walls, orthogonal to the longitudinal axis (X). P023841IT-01 Notarbartolo & Gervasi SpA 4. Apparatus according to claim 3, wherein said at least one lateral end portion (5) has a plurality of through holes (11) defining a respective axis parallel to the longitudinal axis (X), and preferably arranged along a circumference coaxial to said longitudinal axis (X), so that the volume of the respective annular cavity (6) is reduced; or wherein radial reinforcement elements (12) are provided between the two parallel walls such as to divide the annular cavity (6) into a plurality of sectors (60), and wherein at least a first radial hole (9) is provided which connects said internal duct (8) with a respective sector (60), and at least a second radial hole (10) which connects said respective sector to at least one internal channel (3).

5. Apparatus according to any of the preceding claims, wherein said hollow transmission element (7) is a first lateral hub, or a through-axis hub, wherein both lateral end portions (5, 5') of said hollow cylindrical body (1) comprise a respective annular gap (6, 6'); wherein a first annular gap (6) of a first lateral end portion (5) is adapted to receive a heat-transfer fluid from the internal duct (8) of said first lateral hub, or of said through-axis hub, and to distribute it in said at least one internal channel (3); and wherein a second annular gap (6') of a second lateral end portion (5') is adapted to receive said heat-transfer fluid from said at least one internal channel (3) and convey it into a further internal duct (8') of a second lateral hub, or of said through-axis hub, to which said second lateral end portion (5') is connected.

6. Apparatus according to claim 5, wherein the first annular cavity (6) and the second annular cavity (6') are each delimited by two respective parallel walls, orthogonal to the longitudinal axis (X); wherein both lateral end portions (5, 5') have a respective plurality of through holes (11) defining a respective axis parallel to the longitudinal axis (X), and preferably arranged along a circumference coaxial to said longitudinal axis (X), so that the volume of the respective annular cavity (6, 6') is reduced; P023841IT-01 Notarbartolo & Gervasi SpApreferably wherein both lateral end portions (5, 5') are provided with a respective external cover panel (20); wherein said external cover panels (20) are held integral with the respective end portion (5, 5') and held integral with each other by means of a plurality of tie rods (21), each tie rod (21) passing through a respective through hole (11) of each end portion (5, 5').

7. Apparatus according to claim 5, wherein the first annular cavity (6) and the second annular cavity (6') are each delimited by two respective parallel walls, orthogonal to the longitudinal axis (X); wherein both lateral end portions (5, 5') have respective radial reinforcement elements (12) between the two parallel walls such as to divide, respectively, the first annular cavity (6) into a plurality of first sectors (60) and the second annular cavity (6') into a plurality of second sectors, in which at least one first radial hole (9) is provided which connects said internal duct (8) with a respective first sector (60), and at least one second radial hole (10) which connects said respective first sector to at least one internal channel (3);and in which at least a third radial hole is provided which connects said at least one internal channel (3) to a respective second sector, and at least a fourth radial hole which connects said respective second sector to said further internal duct (8'); preferably in which both lateral end portions (5, 5') are provided with a respective external covering panel (20).; 8. Apparatus according to any of the preceding claims, wherein said hollow transmission element (7) is a first lateral hub, or a through-axis hub, and wherein the following are provided: - a fixed pipe (24) for the passage of heat transfer fluid; - a hollow transmission shaft (15) which can be driven by a motor (13), provided inside it with a pipe (16) integral with it and coaxial with the longitudinal axis (X), and integrally connected to said first lateral hub or to said through-axis hub (7) so that pipe (16) and internal duct (8) define a rotating pipe (16, 8); P023841IT-01 Notarbartolo & Gervasi SpA- a rotary joint (18) connecting said fixed pipe (24) to said rotating pipe (16, 8); preferably wherein the rotary joint (18) comprises a fixed part (25), connected to said fixed pipe (24), and a rotating conduit (17) inside said fixed part (25) communicating with said rotating pipe (16, 8); preferably wherein said rotary joint (18) further comprises a conical coupling flange (26) arranged on said rotating conduit (17) and fixed to said hollow transmission shaft (15).

9. Apparatus according to claim 8, wherein the tube (16) is provided in its thickness with an annular air chamber (16').

10. Apparatus according to claim 8 or 9, wherein there are provided - at least one support (19) of the hollow transmission shaft (15), with bearings interposed between said support (19) and said hollow transmission shaft (15); - and a plurality of cooling fins (22), protruding from said hollow transmission shaft (15), arranged between said at least one support (19) and a first end of the hollow transmission shaft (15) connected to said first lateral hub or through-axis hub (7).

11. Apparatus according to claim 8 or 9 or 10, wherein a chain drive (14) is provided, preferably with epicyclic reduction gear, connecting said motor (13) to a second end of said hollow drive shaft (15) connected to the rotary joint (18); preferably wherein a regulation system is provided for adjusting the tension of the chain of said chain drive (14), for example a mechanical or pneumatic or hydraulic actuator.

12. Apparatus according to any of the preceding claims, wherein said at least one internal channel (3) comprises two or three helical channels, preferably connected in parallel, delimited by a respective helical groove (4), made on the external lateral surface of said hollow cylindrical body (1), and by the cylindrical internal radial surface of the external shell (2).

13. Annealing plant for a metal strip advancing along one direction, said plant comprising in succession - at least one preheating section (30); P023841IT-01 Notarbartolo & Gervasi SpA- at least one heating section (31); - at least one temperature maintenance section (32); - at least one cooling section (33); wherein a first heat exchange apparatus according to claim 1 is provided in said at least one preheating section (30); wherein a second heat exchange apparatus according to claim 1 is provided in said at least one cooling section (33); and wherein a closed circuit of heat transfer fluid is provided configured to pass through both said second heat exchange apparatus to remove heat energy from the metal strip by conduction, obtaining high temperature heat transfer fluid, and said first heat exchange apparatus to yield heat energy to the metal strip by conduction, obtaining low temperature heat transfer fluid.

14. Annealing plant according to claim 13, wherein in the first heat exchange apparatus said at least one bridle roll comprises a plurality of heating bridle rolls (34) for advancing the metal strip; wherein in the second heat exchange apparatus said at least one bridle roll comprises a plurality of cooling bridle rolls (35) for advancing the metal strip; wherein said closed circuit of heat transfer fluid passes in series both the cooling bridle rolls (35), provided in said at least one cooling section (33), and the heating bridle rolls (34) provided in said at least one preheating section (30).

15. Annealing plant according to claim 13, wherein both the heating bridle rolls (34) and the cooling bridle rolls (35) are arranged in a configuration such that each bridle roll is wrapped by the metal strip for at least 190°; preferably wherein both in said at least one preheating section (30) and in said at least one cooling section (33) an even number, preferably six, of bridle rolls (34, 35) are provided which are arranged in succession to each other, in groups of two bridle rolls at different heights from each other, preferably only two different heights.