System for drying ceramic products and plant for manufacturing ceramic tiles

Abstract

An air drying system (10) for ceramic products comprises a drying chamber (11), in which green ceramic substrates (SC) are dried, transit means (14) for the controlled passing through of the ceramic substrates (SC) in the chamber (11) and at least one first recirculation duct (16), connected to the chamber (11) and comprising a first fan (12) and a first burner (13) placed in flow communication by means of a first heat exchange device (15) which is operatively connected to a first heating circuit (CR1), supplied by a first source (S1) of a first heat carrier fluid to indirectly transfer heat from the first heat carrier fluid to the air circulating in the first duct (16). The system (10) further comprises a first monitoring and control unit (UMC) adapted to control the first fan (12), the first burner (13) and the transit means (14).

Description

Background of the invention

[0001] The present invention relates to an air-based system for drying ceramic products and a plant for manufacturing ceramic tiles comprising the drying system mentioned above.State of the art

[0002] There is known the use of an air-based dryer in a ceramic products manufacturing process.

[0003] In particular, there is widely known the use of air-based dryers in a ceramic tiles manufacturing process.

[0004] Generally, the ceramic tile manufacturing process starts with the choice of the raw materials which, after being suitably weighed, are ground and atomised so as to obtain a fine and even powder.

[0005] Purely by way of example, in the case of porcelain stoneware ceramic tiles, the raw materials comprise clays, feldspars, kaolins and sand, so as to provide a ceramic tile with high mechanical characteristics and a coefficient of water absorption below 0.5%.

[0006] Subsequently, the powder is made to converge into a press where it is compacted. During the pressing, there is also defined the format of the ceramic tile.

[0007] The ceramic substrate thus obtained is called "green".

[0008] Subsequently, the ceramic substrate is conveyed into the dryer so as to reduce the moisture present therein and, by so doing, make the ceramic substrate (not yet fired) suitable for the subsequent processes of the production process.

[0009] The drying is usually carried out using hot air, continuously blown into the dryer at temperatures by way of example comprised between 110°C and 200°C.

[0010] The blown air is heated using burners.

[0011] Generally speaking, a dryer comprises a drying chamber inside which the green ceramic substrates are dried, transit means for the controlled passing through of the green substrate in the drying chamber and at least one recirculation duct for recirculating hot air in the drying chamber.

[0012] In particular, in the recirculation duct there are placed a fan for the controlled recirculation of air in the drying chamber and at least one burner for the controlled heating of the air, operatively connected to each other.

[0013] In conclusion, a dryer generally also comprises a monitoring and control unit adapted to control the at least one fan, the at least one burner and the transit means.

[0014] The dryer may be of the horizontal type (one-channel or multi-channel) or of the vertical type.

[0015] However, the choice to opt for one or the other often depends on the surface available in the manufacturing cabin (a vertical dryer has smaller overall dimensions in plan view) given that the two types of dryers share the same basic operating principles, using hot air to evenly heat the green ceramic substrate (with high moisture content upon exiting from the pressing machine) and, therefore, reducing the moisture contained therein.

[0016] Once dried, the ceramic substrate is transferred into an glazing line where at least one exposed surface of the aforementioned substrate is decorated.

[0017] In detail, the exposed surface of the substrate is firstly covered with a engobe layer so as to adjust the colour tone thereof and prepare it for a subsequent decoration step in which the decoration is actually carried out.

[0018] In particular, the latter may be applied in various ways known to the person skilled in the art. However, application using ceramic ink digital jet printer is the most advantageous one in terms of customisation of the decoration.

[0019] By way of non-limiting example, a digital printer ceramic ink comprises an inorganic pigment in the form of micrometric particles and dispersed in a liquid which, usually, comprises a solvent (non-polar or polar) together with additives.

[0020] Subsequently, there is applied a protection layer on the decoration and the ceramic substrate, which after this step is also referred to as "raw tile", is subjected to a controlled firing process.

[0021] By way of non-limiting example, the protection layer usually comprising a layer of glaze. However, the protection layer may also comprise grits (dry or dispersed in an glaze).

[0022] In particular, firing is carried out in special roller kilns at temperatures of about 1230°C in the case of porcelain stoneware ceramic tiles and the duration of the firing process varies depending on the format and the thickness of the raw tile entering into the kiln.

[0023] Post-firing, the ceramic tile may be subjected to a grinding step, in which it is squared and dimensioned under a calibre, and then packaged and ready for selling on the market.

[0024] Furthermore, should one intend to obtain a structured tile, that is a ceramic tile which has a 3D structure at the exposed surface, the person skilled in the art may choose from among various solutions, which can be combined with each other.

[0025] In particular, a solution consists in obtaining a structured ceramic substrate upon exiting from the pressing step positioning a mould, which has the negative of the 3D structure intended to be obtained on the exposed surface of the ceramic substrate, in the pressing machine.

[0026] However, the solution mentioned above results in the required replacement of the mould whenever there arises the need to change the 3D structure, clearly wasting time.

[0027] Therefore, the solution mentioned above is increasingly no longer used and, nowadays, the ceramic tiles are typically structured through: i) the application, by means of digital jet printer, of a liquid called "reserving agent"; ii) the application, by means of digital jet printer, of a liquid called "sinking agent"; iii) the application, by means of digital jet printer, of an adhesive liquid on which the grit is deposited.

[0028] As a matter of fact, the solutions mentioned above allow to obtain a 3D structure in a more efficient and customisable manner given that one is no longer bound to a physical mould but rather to a digital model stored in the digital printer and which can be managed by the same.

[0029] In detail, the expression "reserving agent" is generally used to indicate a compound which "opens" or "shreds" the glaze (or engobe) applied thereon.

[0030] As a matter of fact, the reserving agent is a compound which interacts with the glaze (or engobe), for example with the carrier contained in the glaze (or engobe), repelling it, therefore, defining recesses in the surface of the overlying glaze (or engobe).

[0031] In particular, in this event, there is used a polar reserving agent (that is containing a polar substance) if the carrier of the glaze (or engobe) is of the non-polar type. Vice versa, there is used a non-polar reserving agent (that is containing a non-polar substance) when the carrier of the glaze (or engobe) is of the polar type.

[0032] Otherwise, the expression "sinking agent" is generally used to indicate a compound which "sinks" into the underlying glaze (or engobe) or "it sinks" the overlying glaze (or engobe).

[0033] In particular, the sinking agent is a compound which, interacting with the underlying or overlying glaze (or engobe), modifies the crystalline structure thereof during the firing step, forming recesses in the surface of the glaze (or engobe).

[0034] It should be observed that both the use of a sinking agent to form recesses in the surface of the glaze (or engobe); on the other hand, the solution iii) allows to create reliefs on the surface of the glaze (or engobe) given that, during firing, the grit is sintered and welded to the ceramic substrate.

[0035] The short description outlined above relating to a typical ceramic tile manufacturing process, clearly shows that energy consumption for manufacturing ceramic tiles is rather high and, therefore, right from the eighties plant engineers and manufacturers have focused on developing technological innovations adapted to improve the energy efficiency of ceramic manufacturing processes.

[0036] In particular, one of the most energy consuming steps is the drying step given that the amount of gaseous fuel required for heating the drying air still remains the highest one.

[0037] Therefore, it would be desirable to provide a solution which allows to reduce the environmental impact of the ceramic industry.

[0038] In particular, it would be desirable to provide a solution capable of reducing the consumption of gaseous fuel during the ceramic tiles drying process.Objects of the invention

[0039] An object of the present invention is to reduce the environmental impact of the ceramic industry.

[0040] A further object of the present invention is to provide a system for drying ceramic products which has low consumption of gaseous fuel.

[0041] An additional object of the present invention is to provide a plant for manufacturing ceramic tiles which has low consumption of gaseous fuel.Brief description of the invention

[0042] These and other objects which will be apparent to a person skilled in the art are attained by means of a system for drying ceramic products and a plant for manufacturing ceramic tiles according to the invention.

[0043] As mentioned above, in a first aspect thereof, the invention relates to a system for drying ceramic products which comprises a drying chamber, within which green ceramic substrates are dried, transit means for the controlled passing through of the green ceramic substrates in the drying chamber and at least one first recirculation duct for recirculating hot air in the drying chamber.

[0044] The drying chamber comprises an inlet, through which the green ceramic substrates enter into the drying chamber and an outlet, through which the dried ceramic substrates exit from the drying chamber.

[0045] The drying chamber also comprises at least one first air inlet opening and a first air outlet opening adapted to place in flow communication the interior of the drying chamber with the first recirculation duct.

[0046] The geometry of the drying chamber may vary. However, there can be identified two macro-categories of drying chambers.

[0047] The first macro-category includes "vertical" drying chambers, that is chambers which have vertical overall dimensions greater than the one in plan view, while the second macro-category includes the "horizontal" drying chambers, which unlike the previous ones have over in plan view greater than the vertical one.

[0048] The choice to opt for the first or second type usually depends on the surface available in the manufacturing cabin.

[0049] It is clear that the trajectory described in the drying chamber by the transit means, and therefore by the green ceramic substrates, depends on the geometry of the drying chamber.

[0050] By way of example, the transit means comprise a plurality of horizontal surfaces designed to support the green ceramic substrates and convey them sliding along a guide, from the inlet of the drying chamber to the outlet of the drying chamber.

[0051] In particular, the first recirculation duct comprises a first fan, for recirculating air in the drying chamber, and a first burner, for heating air, operatively connected to each other.

[0052] Preferably, the fan is positioned upstream of the burner.

[0053] The system also comprises a monitoring and control unit adapted to control the first fan and the first burner.

[0054] This allows to control the flow rate and the temperature of the air flowing out from the first recirculation duct which, by way of example, is comprised between 110°C and 200°C.

[0055] In particular, the ideal temperature flowing out from the first recirculation duct may vary depending on the characteristics of the green ceramic substrate such as the composition (raw materials used and the relevant weight) and size of the green ceramic substrate (that is the format of the green ceramic substrate).

[0056] Therefore, it may be advantageous to provide the monitoring and control unit with a physical storage device or connect it to a cloud storage so as to generate (and store) a database in which there are stored the various temperature set points paired to the compositions and to the format of the green ceramic substrate.

[0057] Preferably, the first recirculation duct further comprises a first temperature sensor, positioned along the first recirculation duct and arranged downstream of the first burner so as to control the temperature of the air flowing out from the latter.

[0058] In particular, the first temperature sensor is operatively connected to the monitoring and control unit.

[0059] The first recirculation duct also comprises a first heat exchange device adapted to place in flow communication the first fan and the first burner, and operatively connected to a first heating circuit, inside which there circulates a first heat carrier fluid displaced by a first pumping system, for transferring heat from the first heat carrier fluid to the air flowing out from the fan.

[0060] By way of example, the first heat carrier fluid is water.

[0061] By way of non-limiting example, the first heat exchange device is selected from a group comprising heat exchangers of the tube bundle and jacket type, plate heat exchangers and spiral heat exchangers.

[0062] The first heat exchange device transfers the heat from the first heat carrier fluid to the air flow to be heated indirectly, that is without direct contact between the first heat carrier fluid and the air flow to be heated.

[0063] Optionally, the cross-section of the first recirculation duct at the first heat exchange device is larger than the cross-section of the first recirculation duct at the first fan and the cross-section of the first recirculation duct at the first burner.

[0064] Besides allowing to slow the air at the first heat exchange device, thus making the heat exchange more effective, this characteristic also allows to increase the heat exchange surface, therefore increasing the exchangeable power.

[0065] Optionally, the first heat exchange device is configured to cover a percentage comprised between 50% and 90% of the average load of the first burner operatively connected thereto.

[0066] Preferably, a percentage comprised between 60% and 80%.

[0067] As a matter of fact, such approach allows the first heat exchange device to provide a constant thermal power, therefore ensuring an efficient thermal recovery, and at the same time rapidly meet the sudden thermal power changes required through the first burner.

[0068] In this case, it is preferable that the first recirculation duct comprises, besides the first temperature sensor, also a second temperature sensor, positioned downstream of the first heat exchange device and upstream of the first burner so as to control the temperature of the air flowing out from the first heat exchange device and, therefore, the percentage of the average load of the first burner covered by the first heat exchange device.

[0069] In particular, the second temperature sensor and the first pumping system of the first heating circuit may be operatively connected to the monitoring and control unit designed to control the flow rate of the first heat carrier fluid depending on the temperature detected by the first temperature sensor and by the second temperature sensor.

[0070] However, it is clear that there may be provided for a second monitoring and control unit designed to control the flow rate of the first heat carrier fluid. In this event, the two monitoring and control units should be operatively connected so as to coordinate their actions.

[0071] For example, if the temperature measured by the first temperature sensor is too low (for example, it is equal to 100°C) and the first heat exchange device is covering 40% of the average load of the first burner, then the monitoring and control unit will command the first pumping system to increase the flow rate of the first heat carrier fluid so as to raise the temperature of the air flowing out from the first burner without increasing the consumption of gaseous fuel by the first burner. Otherwise, if the temperature measured by the first temperature sensor is too low (for example, equal to 100°C) and the first heat exchange device is covering 90% of the average load of the burner, then the monitoring and control unit will increase the activity of the first burner (that is, it will increase the consumption of gaseous fuel) so as to increase the temperature of the air flowing out from the latter.

[0072] Optionally, the first recirculation duct comprises a first bypass sub-duct along which there is positioned a bypass valve which can be remote-controlled by means of the monitoring and control unit for by-passing, if need be, the first heat exchange device, therefore placing in direct flow communication the first fan and the first burner.

[0073] In this case, the first recirculation duct also comprises a first exclusion valve and a second exclusion valve, which can be controlled by means of the monitoring and control unit, positioned so as to exclude the first heat exchange device.

[0074] In particular, the first exclusion valve is positioned between the first fan and the first heat exchange device and the second exclusion valve is positioned between the first heat exchange device and the first burner.

[0075] Optionally, the first heating circuit is supplied by a first source of heat carrier fluid configured to supply the first heating circuit with a first heat carrier fluid at a temperature comprised between 100°C and 180°C.

[0076] Preferably, the temperature of the first heat carrier fluid flowing into the heat exchange device is comprised between 120°C and 160°C.

[0077] Optionally, the first fan is of the type supplied through an inverter.

[0078] This further characteristic allows to more easily compensate for the greater pressure drops introduced by the first heat exchange device and effectively adjust the drying system.

[0079] The system for drying ceramic products according to the invention may also comprise at least one second recirculation duct for recirculating hot air in the drying chamber.

[0080] This solution may be particularly adapted to provide a controlled and effective drying step even when the size of the drying chamber (and therefore the volume within which there arises the need to ensure an air temperature comprised, by way of example, between 110°C and 200°C) are particularly high.

[0081] In this case, the drying chamber also comprises at least one second air inlet opening and a second air outlet opening adapted to place in flow communication the interior of the drying chamber with the second recirculation duct.

[0082] In particular, in a first version, the second recirculation duct comprises a second fan, for the controlled recirculation of air in the drying chamber, and a second burner, for the controlled heating of air, operatively connected to each other.

[0083] In particular, the monitoring and control unit is adapted to also control the second fan and the second burner.

[0084] The second recirculation duct may further comprise a third temperature sensor, arranged downstream of the second burner so as to control the temperature of the air flowing out from the latter.

[0085] In detail, the monitoring and control unit is operatively connected to the third temperature sensor.

[0086] This allows to also control the flow rate and the temperature of the air flowing out from the second recirculation duct which, by way of example, is comprised between 110°C and 200°C.

[0087] In a second version, the second recirculation duct also comprises a second heat exchange device adapted to place in flow communication the second fan and the second burner, and operatively connected to a second heating circuit, inside which there circulates a second heat carrier fluid displaced by a second pumping system, for transferring heat from the second heat carrier fluid to the air flowing out from the second fan.

[0088] In this case, the second fan is preferably positioned upstream of the second burner.

[0089] By way of example, the second heat carrier fluid is water.

[0090] By way of non-limiting example, the second heat exchange device is selected from a group comprising tube bundle and jacket heat exchangers, plate heat exchangers and spiral heat exchangers.

[0091] The second heat exchange device transfers the heat from the second heat carrier fluid to the air flow to be heated indirectly, that is without direct contact between the second heat carrier fluid and the air flow to be heated.

[0092] Optionally, the cross-section of the second recirculation duct at the second heat exchange device is larger than the cross-section of the second recirculation duct at the second fan and the cross-section of the second recirculation duct at the second burner.

[0093] Optionally, the second heat exchange device is configured to cover a percentage comprised between 50% and 90% of the average load of the second burner.

[0094] Preferably, a percentage comprised between 60% and 80%.

[0095] In this case, it is preferable that the second recirculation duct comprises, besides the third temperature sensor, also a fourth temperature sensor, positioned downstream of the second heat exchange device and upstream of the second burner so as to control the temperature of the air flowing out from the second heat exchange device.

[0096] In particular, the fourth temperature sensor and the second pumping system of the second heating circuit may be operatively connected to the monitoring and control unit so as to control the flow rate of the second heat carrier fluid depending on the temperature detected by the third temperature sensor and by the fourth temperature sensor as described above with regard to the first recirculation duct.

[0097] However, it is clear that there may be provided for a further monitoring and control unit designed to control the flow rate of the second heat carrier fluid. In this event, the two monitoring and control units should be operatively connected so as to coordinate their actions.

[0098] Optionally, the second recirculation duct comprises a first bypass sub-duct along which there is positioned a second bypass valve which can be remote-controlled by means of the monitoring and control unit for by-passing, if need be, the second heat exchange device, therefore placing in direct flow communication the second fan and the second burner.

[0099] In this case, the second recirculation duct also comprises a third exclusion valve and a fourth exclusion valve, which can be controlled by means of the monitoring and control unit, positioned so as to exclude the second heat exchange device.

[0100] In particular, the third exclusion valve is positioned between the second fan and the second heat exchange device and the fourth exclusion valve is positioned between the second heat exchange device and the second burner.

[0101] Optionally, the second heating circuit is supplied by the first source of heat carrier fluid.

[0102] In this case, the first heat carrier fluid coincides with the second heat carrier fluid.

[0103] Alternatively, the second heating circuit may be supplied both by a second source of heat carrier fluid configured to supply the second heating circuit with a second heat carrier fluid at a temperature comprised between 100°C and 180°C.

[0104] Preferably, the temperature of the second heat carrier fluid flowing into the heat second exchange device is comprised between 120°C and 160°C.

[0105] Optionally, the second fan is of the type supplied through an inverter as described above with regard to the first recirculation duct.

[0106] Optionally, the first source of heat carrier fluid and / or the second source of heat carrier fluid comprises a heat exchange equipment configured to transfer heat from the combustion fumes, and / or the air for cooling the tiles, of a ceramic kiln to the first heat carrier fluid and / or second heat carrier fluid respectively circulating in the first heating circuit and of the second heating circuit.

[0107] Optionally, the heat exchange equipment comprises a heat-pipe heat exchanger configured to transfer heat from the combustion fumes of a ceramic kiln to the first heat carrier fluid and / or second heat carrier fluid.

[0108] Optionally, the heat exchange equipment comprises a finned pack exchanger configured to transfer heat from the air for cooling the tiles of a kiln to the first heat carrier fluid and / or second heat carrier fluid.

[0109] In a second aspect thereof, the invention relates to a plant for manufacturing ceramic tiles.

[0110] The plant comprises (i) a ceramic pressing station, at which a ceramic powder is compacted to form a green ceramic substrate, (ii) a drying station, at which the green ceramic substrate is dried, (iii) a decoration station, at which an exposed surface of the dried green ceramic substrate is decorated and (iv) a firing station, at which the decorated ceramic substrates are fired.

[0111] In particular, the drying station comprises a drying system comprising one or more of the characteristics outlined above with reference to the first aspect of the invention.

[0112] The plant for manufacturing ceramic tiles further comprises transport means configured to transport the ceramic substrates from one station to the subsequent one along an advancement direction.

[0113] By way of non-limiting example, the transport means comprise a conveyor belt movable along the aforementioned advancement direction.

[0114] By way of non-limiting example, the pressing station comprises a pressing machine adapted to compact a ceramic powder obtained from the grinding and atomisation of ceramic raw materials (which vary in terms of quantity and type depending on the desired composition of the green ceramic substrate) and therefore define the format of the green ceramic substrate.

[0115] Should one intend to obtain a three-dimensional structure at the exposed surface of the ceramic substrate, a mould, which has the negative of the desired three-dimensional structure, can be placed in the pressing machine, as known by the person skilled in the art.

[0116] By way of non-limiting example, the decoration station comprises: an airbrush provided with a plurality of airless nozzles adapted to evenly deposit a layer of engobe on the exposed surface of the dried ceramic substrate so as to adjust the colour tone thereof so as to provide the decoration; a ceramic digital ink jet printer for obtaining the decoration; an airbrush provided with a plurality of airless nozzles adapted to deposit a protection layer on the decorated exposed surface.

[0117] By way of non-limiting example, the protection layer usually comprising a layer of glaze. However, the protection layer may also comprise grits (dry or dispersed in an glaze).

[0118] Should one intend to obtain a three-dimensional structure at the exposed surface of the ceramic substrate, in the decoration station there can be placed a digital jet printer for a liquid called "reserving agent", that is a compound which "opens" or "shreds" the glaze (or engobe) applied thereon.

[0119] Optionally, the digital printer for a reserving liquid may be the same used to provide the decoration, as known by the person skilled in the art.

[0120] As a matter of fact, basically it suffices to replace a printer head of the ceramic ink jet digital printer with a head adapted to print a reserving liquid considering the different rheological characteristics of the liquids.

[0121] In order to obtain a three-dimensional structure at the exposed surface of the ceramic substrate, in the decoration station there can also be placed a digital jet printer for a liquid called "sinking agent", that is a compound which "sinks" into the underlying glaze (or engobe) or "it sinks" the overlying glaze.

[0122] Optionally, the digital printer for a sinking liquid may be the same used to provide the decoration, as known by the person skilled in the art.

[0123] Furthermore, still with the aim of obtaining a three-dimensional structure at the exposed surface of the ceramic substrate, in the decoration station there can be placed a digital jet printer for an adhesive liquid followed by a gritting machine, or more simply a hopper, for depositing a grit layer, and an extractor hood (or a technical equivalent thereof) for removing the grit that has not adhered to the adhesive liquid.

[0124] In particular, the station comprises a ceramic kiln.

[0125] By way of non-limiting example, the ceramic kiln is a roller ceramic kiln configured to fire the ceramic substrates at maximum temperatures which can reach 1250-1300 °C (firing temperature of the porcelain stoneware ceramic tiles).

[0126] Optionally, the first source of heat carrier fluid and / or the second source of heat carrier fluid comprises a heat exchange equipment configured to transfer heat from the combustion fumes, and / or the air for cooling the tiles, of the ceramic kiln of the plant to the first heat carrier fluid and / or second heat carrier fluid respectively circulating in the first heating circuit and of the second heating circuit.

[0127] Optionally, the heat exchange equipment comprises a heat-pipe heat exchanger configured to transfer heat from the combustion fumes of the ceramic kiln of the plant to the first heat carrier fluid and / or second heat carrier fluid.

[0128] Optionally, the heat exchange equipment comprises a finned pack exchanger configured to transfer heat from the air for cooling the tiles of the kiln of the plant to the first heat carrier fluid and / or second heat carrier fluid.

[0129] Optionally, the plant for manufacturing ceramic tiles comprises a grinding station placed downstream of the advancement direction, of the firing station.

[0130] By way of non-limiting example, the grinding station comprises a dry automated edging machine.Brief description of the drawings

[0131] The invention will be clearer and implemented with reference to the to the attached drawings which show an exemplifying and non-limiting embodiment thereof, wherein: figure 1 schematically shows a first embodiment of a drying system according to the invention; figure 2 schematically shows the drying system of figure 1 with operative connections specified; figure 3 is a perspective view, in enlarged scale, of the external of a device of the system of figure 1; figure 4 is a lateral cross-sectional view of figure 3; figure 5 schematically shows, in smaller scale, the drying system of figure 1 with additional elements; figure 6 schematically shows a second embodiment of a drying system according to the invention; figure 7 schematically shows a third embodiment of a drying system according to the invention. figure 8 schematically shows a plant for manufacturing ceramic tiles according to the invention; figure 9 is a schematic view of the internal of a heat-pipe heat exchanger; figure 10 is a schematic top view of a finned pack exchanger; figure 11 is a front view of figure 10. Detailed description of the invention

[0132] With reference to the figures 1 and 2, herein described is a first embodiment, provided by way of non-limiting example, of a drying system 10 according to the invention.

[0133] In particular, the system 10 comprises a drying chamber 11, designed to be fixed to the floor during use, inside which there are dried green ceramic substrates SC, transit means 14 for the controlled passing through of the green ceramic substrates SC in the chamber 11 and two recirculation ducts 16,16' for recirculating hot air in the chamber 11.

[0134] In detail, as shown in figures 3 and 4, the chamber 11 comprises an inlet 19, through which the green ceramic substrates SC enter into the drying chamber 11, and an outlet 20, through which the dried ceramic substrates SC exit from the drying chamber 11.

[0135] The geometry of the chamber 11 may vary. However, there can be identified two macro-categories of the chambers 11 and it is clear that the trajectory described in the chamber 11 by transit means 14, and therefore by green ceramic substrates SC, depends on the geometry of the chamber 11.

[0136] In particular, the transit means 14 comprise a plurality of horizontal surfaces 14a designed to support the green ceramic substrates SC and convey them, sliding along a guide 14b, from the inlet 19 to the outlet 20 following the trajectory mentioned above.

[0137] In detail, the chamber 11 is of the vertical type.

[0138] In particular, the chamber 11 has outer side walls 21-24, a base 25 and a ceiling 26 arranged substantially to form a parallelepiped shape (hollow).

[0139] Even more particularly, the inlet 19 and the outlet 20 are obtained at two opposite outer side walls 21-24.

[0140] Hereinafter, the side wall which houses the inlet 19 will be renamed input wall 21 while the side wall which houses the outlet 20 will be renamed output wall 23.

[0141] Even more particularly, in the embodiment, provided by way of example, of figures 1 to 4, the chamber 11 comprises two volumes: an ascent volume 11a and a descent volume 11b.

[0142] As a matter of fact, in the vertical chamber 11, the transit means 14, and therefore the green ceramic substrates SC arranged thereon, describe a trajectory comprising an ascent section TS, which substantially extends from the inlet 19 to the ceiling 26, a descent section TD which substantially extends from the ceiling 26 to the outlet 20.

[0143] Therefore, the ascent section TS, is contained in the ascent volume 11a while the descent section TD is contained in the descent volume 11b.

[0144] In the non-limiting embodiment of figures 1-4, the first recirculation duct 16 defines a first air recirculation which predominantly affects the ascent volume 11a while the second recirculation duct 16' defines a second air recirculation which predominantly affects the descent volume.

[0145] Even more particularly, the first recirculation duct 16 is connected inside the chamber 11 by means of a first air inlet opening 27, positioned at the input wall 21, and a first air outlet opening 28, positioned at one of the outer side walls 22,24 adjacent to the input wall 21.

[0146] Preferably, the first air inlet opening 27 is positioned above the inlet 19, as shown in figure 3 and 4.

[0147] Otherwise, the second recirculation duct 16' is connected inside the chamber 11 by means of a second air inlet opening 27', positioned at the output wall 23, and a second air outlet opening 28', positioned at one of the outer side walls 22,24 adjacent to the output wall 23.

[0148] Preferably, the second air inlet opening 27' is positioned above the outlet 20, as shown in figure 3 and 4.

[0149] Advantageously, the first air outlet opening 28 and the second air outlet opening 28' are obtained at two opposite outer side walls.

[0150] In particular, the first recirculation duct 16 comprises a first fan 12 for the controlled recirculation of air inside the chamber 11, and a first burner 13, for the controlled heating of the air, operatively connected to each other.

[0151] The first fan 12 is positioned upstream of the after burner 13.

[0152] The first recirculation duct 16 further comprises a first temperature sensor 35, positioned along the first recirculation duct 16 and arranged downstream of the first burner 13 so as to control the temperature of the air flowing out from the latter.

[0153] In the specific embodiment of figures 1 and 2, the first recirculation duct 16 also comprises a first heat exchange device 15 adapted to place in flow communication the first fan 12 and the first burner 13, and operatively connected to a first heating circuit CR1, inside which there circulates a first heat carrier fluid, for transferring heat from the first heat carrier fluid to the air flowing out from the first fan 12.

[0154] In particular, the first heat carrier fluid is water.

[0155] In this regard, the first fan 12 is of the type supplied by means of an inverter so as to easily compensate for the greater pressure drops introduced by the first device 15 and effectively adjust the system 10.

[0156] In detail, the first heating circuit CR1 is supplied by a first source S1 of hot water and it comprises a first hot portion CR1a, inside which there flows the hot water (that is, the water flowing out from the first source S1), and a first cold portion CR1b, inside which there flows the cold water (that is, the heat carrier water flowing out from the heat exchange device 15).

[0157] The first heating circuit CR1 further comprises a first pumping system 29 adapted to flow the water from the first source S1 to the first device 15, and vice versa, at a determined flow rate.

[0158] In detail, the first source S1 is configured to supply the first heating circuit CR1 with water at a temperature comprised between 100°C and 180°C.

[0159] In particular, the first device 15 comprises an air inlet opening 15a, through which the air suctioned by the first fan 12 flows into the first device 15, and an air outlet opening 15b, through which air flows out from the first device 15 and it is directed to the first burner 13.

[0160] Furthermore, the first device 15 comprises a water inlet opening 15c and a water outlet opening 15d which connect it to the first heating circuit CR1.

[0161] Therefore, the first hot portion CR1a of the first heating circuit CR1 extends from the first source S1 to the water inlet opening 15c of the first device 15.

[0162] Vice versa, the first cold portion CR1b of the first heating circuit CR1 extends from the water outlet opening 15d of the first device 15 to the first source S1.

[0163] As shown in figures 1 and 2, the cross-section A1 of the first recirculation duct 16, at the first device 15 is larger than the cross-section A2 of the first recirculation duct 16 at the first fan 12 and the cross-section A3 of the first recirculation duct 16 at the first burner 13 so as to make the heat exchange more effective and allow to increase the heat exchange surface.

[0164] In particular, the first device 15 transfers heat from the water to the air flow to be heated indirectly, that is without direct contact between the water and the air flow.

[0165] In the particular non-limiting embodiment described herein, the first device 15 is a heat-pipe heat exchanger.

[0166] This document does not aim at providing a detailed description of a heat-pipe heat exchanger, just like it does not aim at providing a detailed description of the operation thereof.

[0167] However, a general description thereof is provided hereinafter.

[0168] Generally, as schematised in figure 9, a heat-pipe heat exchanger 150 comprises a main body 151 partitioned into two chambers 151a, 151b, primary and secondary, separated from each other by a separation plate 152 adapted to prevent contact between the contents of the two chambers 151a,151b.

[0169] As a matter of fact, the contents of the primary chamber 151a communicate with the contents of the secondary chamber 151b only thermally by means of a plurality of heat tubes 153 which pass through the aforementioned separation plate 152.

[0170] Therefore, each tube of said plurality has an end which lies in the primary chamber 151a and the other end which lies in the secondary chamber 151b.

[0171] In particular, each pipe of the aforementioned plurality contains a working fluid which carries the heat transfer.

[0172] Considering, for the sake of description simplicity, the use thereof for transferring heat from the water circulating in the first heating circuit CR1 to the air passing through the first recirculation duct 16, the primary chamber 151a comprises the water inlet opening 154 and a water outlet opening 155, while the secondary chamber 151b comprises the air inlet opening 156 and the air inlet opening 157.

[0173] Therefore, the hot water coming from the first source S1 is conveyed into the primary chamber 151a through the water inlet opening 154, it transfers heat to the plurality of heat tubes 153 and then flows out from the primary chamber 151a through the water outlet opening 155.

[0174] Otherwise, the air flows into the secondary chamber 151b through the air inlet opening 156, it absorbs heat from the plurality of heat pipes 153 (heat supplied by the hot water) and then it flows out from the secondary chamber 151b through the water outlet opening 157.

[0175] In detail, the heat is transferred exploiting a phase change of the working fluid which, cyclically, condensates (transferring heat to the air) at the end arranged in the secondary chamber 151b and evaporates (absorbing heat from the water) at the end arranged in the primary chamber 151a.

[0176] In detail, the heat-pipe heat exchanger 150 is particularly adapted given that the heat pipes 153 do not require any maintenance and any failure on some heat pipes 153 does not excessively affect the overall performance of the exchanger.

[0177] In the particular embodiment described herein, the first source S1 comprises a heat exchange equipment configured to transfer heat from the combustion fumes, and / or the air for cooling the tiles, of a ceramic kiln to the water circulating in the first heating circuit.

[0178] In particular, the heat exchange equipment may comprise heat-pipe heat exchanger configured to transfer heat from the combustion fumes of a ceramic kiln.

[0179] As a matter of fact, the temperature of the combustion fumes of a ceramic kiln is about 250°C.

[0180] For the sake of description brevity, reference shall be made to the description above of a heat-pipe heat exchanger.

[0181] Alternatively, the heat exchange equipment may comprise a finned pack exchanger configured to transfer heat from the air for cooling the tiles of a ceramic kiln.

[0182] As a matter of fact, the temperature of the air for cooling the tiles of a ceramic kiln is about 250°C.

[0183] This document does not aim at providing a detailed description of a finned pack exchanger, just like it does not aim at providing a detailed description of the operation thereof.

[0184] However, a general description thereof is provided hereinafter.

[0185] Generally, as schematised in figures 10 and 11, a finned pack exchanger 160 comprises a plurality of fins 162 passed through by a plurality of pipes 161, connected to each other.

[0186] In particular, the material used for obtaining the fins has a lower thermal conductivity with respect to the one used for obtaining pipes.

[0187] In detail, considering the use thereof for transferring heat from the air for cooling tiles to the water circulating in the first heating circuit CR1, the cold water flows through an inlet pipe 163 and flows out, hot, from the outflow pipe 164.

[0188] It should be observed that figure 10 shows the flow of the water with the solid line arrows, while figure 11 shows the flow of the air for cooling the tiles with the dotted line arrows.

[0189] As a matter of fact, as shown in the figures, while the water flows in the plurality of pipes 161, the air for cooling the tiles flow through the fissures 165 defined between the fins and the pipes.

[0190] By so doing, not only does the cooling air transfer heat to the plurality of pipes 161 but also to the plurality of fins 162, therefore increasing the heat transfer efficiency.

[0191] In the embodiment of figures 1 and 2, the second recirculation duct 16' comprises a second fan 12' for the controlled recirculation of air inside the chamber 11, and a second burner 13', for the controlled heating of the air, operatively connected to each other.

[0192] The second recirculation duct 16' further comprises a third temperature sensor 35' positioned along the second recirculation duct 16' and arranged downstream of the second burner 13' so as to control the temperature of the air flowing out from the latter.

[0193] As shown in figures 1 and 2, in the first non-limiting embodiment, the system 10 further comprises a monitoring and control unit UMC adapted to control at least the fans 12,12', the burners 13,13' and the transit means 14.

[0194] In particular, the monitoring and control unit UMC is also operatively connected to the first temperature sensor 35 and to the third temperature sensor 35'. This allows to control the flow rate and the temperature of the air flowing out from the recirculation ducts 16,16' which, by way of example, is comprised between 110°C and 200°C.

[0195] In particular, the ideal temperature of the drying air may vary depending on the characteristics of the green ceramic substrate SC such as the composition (raw materials used and the relevant weight) and size of the green ceramic substrate SC (that is the format of the green ceramic substrate SC).

[0196] Therefore, it may be advantageous to provide the monitoring and control unit UMC with a physical storage device or connect it to a cloud storage so as to generate (and store) a database in which there are stored the various temperature set points paired to the compositions and to the format of the green ceramic substrate SC.

[0197] In the embodiment of figures 1 and 2, the first device 15 is configured to cover a percentage comprised between 50% and 90% of the average load of the first burner 13 so as to allow the first device 15 to provide a constant thermal power and at the same time rapidly meet the sudden thermal power changes required by the first burner 13.

[0198] Therefore, the first recirculation duct 16, also comprises a second temperature sensor 35, positioned downstream of the first device 15 and upstream of the first burner 13 so as to control the temperature of the air flowing out from the first device 15 and, therefore, the percentage of the average load of the first burner 13 covered by the first device 15.

[0199] In particular, as shown in figure 2, the monitoring and control unit UMC is operatively connected to the second temperature sensor 33 and to the first pumping system 29 so as to control the water flow rate depending on the temperature detected by the first temperature sensor 35 and by the second temperature sensor 33.

[0200] For example, if the temperature measured by the first temperature sensor 35 is too low (for example, it is equal to 100°C) and the first device 15 is covering 40% of the average load of the first burner 13, then the monitoring and control unit UMC will command the first pumping system 29 to increase the flow rate of the first heat carrier fluid so as to raise the temperature of the air flowing out from the first burner 13 without increasing the consumption of gaseous fuel by the first burner 13. Otherwise, if the temperature measured by the first temperature sensor 35 is too low (for example, equal to 100°C) and the first device 15 is covering 90% of the average load of the burner, then the monitoring and control unit UMC will increase the activity of the first burner 13 (that is, it will increase the consumption of gaseous fuel) so as to increase the temperature of the air flowing out from the latter.

[0201] In a non-limiting embodiment, shown in figure 5, the first recirculation duct 16 comprises a first bypass sub-duct 30 along which there is positioned a first bypass valve 34 which can be remote-controlled by means of the monitoring and control unit UMC for by-passing, if need be, the first device 15, therefore placing in direct flow communication the first fan 12 and the first burner 13.

[0202] In this variant, the first recirculation duct 16 also comprises a first exclusion valve 31 and a second exclusion valve 32, which can be controlled by means of the monitoring and control unit UMC, positioned so as to exclude the first device 15.

[0203] In particular, the first exclusion valve 31 is positioned between the first fan 12 and the first device 15 and the second exclusion valve 32 is positioned between the first device 15 and the first burner 13.

[0204] Now, with reference to figures 6 and 7, the second recirculation duct 16' also comprises a second heat exchange device 15' adapted to place in flow communication the second fan 12' and the second burner 13', and operatively connected to a second heating circuit CR2, inside which there circulates a second heat carrier fluid, for transferring heat from the second heat carrier fluid to the air flowing out from the second fan 12'.

[0205] In particular, the second the fan 12' is positioned upstream of the second burner 13'.

[0206] In particular, the second heat carrier fluid is water.

[0207] In this regard, the second fan 12' is of the type supplied by means of an inverter so as to easily compensate for the greater pressure drops introduced by the second heat exchange device 15' and effectively adjust the system 10.

[0208] In the non-limiting embodiment of figure 7, the second heating circuit CR2 is supplied by the first source S1.

[0209] Therefore, in this case, the second heating circuit CR1 therefore comprises a first hot portion CR2a, inside which there flows the hot water (that is, the water flowing out from the first source S1), and a second cold portion CR2b, inside which there flows the cold water (that is, the water flowing out from the second device 15').

[0210] Otherwise, in the non-limiting embodiment of figure 6, the second heating circuit CR2 is supplied by a second source S2 a hot water.

[0211] Therefore, in this case, the second heating circuit CR2, therefore, comprises a first hot portion CR2a, inside which there flows the hot water (that is, the water flowing out from the second source S2), and a second cold portion CR2b, inside which there flows the cold water (that is, the water flowing out from the second device 15').

[0212] In detail, the second source S2 is configured to supply the second heating circuit CR2 with water at a temperature comprised between 100°C and 180°C.

[0213] In the particular embodiment of figure 6, the second source S2 comprises a further heat exchange equipment configured to transfer heat from the combustion fumes, and / or the air for cooling the tiles, of a ceramic kiln to the water circulating in the second heating circuit.

[0214] In particular, the heat exchange equipment may comprise a further heat-pipe heat exchanger configured to transfer heat from the combustion fumes of a ceramic kiln.

[0215] For the sake of description brevity, reference shall be made to the description above of a heat-pipe heat exchanger.

[0216] Alternatively, the heat exchange equipment may comprise a further finned pack exchanger configured to transfer heat from the air for cooling the tiles of a ceramic kiln.

[0217] For the sake of description brevity, reference shall be made to the description above of a finned pack heat exchanger.

[0218] The second heating circuit CR2 further comprises a second pumping system 29' adapted to flow the water from the first source S1 (or from the second source S2) to the second device 15', and vice versa, at a determined flow rate.

[0219] As described above with regard to the first device 15, the second device 15' comprises an air inlet opening 15'a, through which the air suctioned by the second fan 12' flows into the second device 15', and an air outlet opening 15'b, through which air flows out from the second device 15' and it is directed to the second burner 13'.

[0220] Furthermore, the second device 15' also comprises a water inlet opening 15'c and a water outlet opening 15'd which connect it to the second heating circuit CR2.

[0221] Therefore, the second hot portion CR2a of the second heating circuit CR2 extends from the first source S1 (or from the second source S2) to the water inlet opening 15'c of the second device 15' while the second cold portion CR2b of the second heating circuit CR2 extends from the water outlet opening 15'd of the second device 15' to the first source S1 (or to the second source S2).

[0222] Furthermore, in the particular embodiments of figures 6 and 7, the cross-section A1' of the second recirculation duct 16', at the second device 15' is larger than the cross-section A2' of the second recirculation duct 16' at the second fan 12' and the cross-section A3' of the second recirculation duct 16' at the second burner 13 so as to make the heat exchange more effective and allow to increase the heat exchange surface.

[0223] In particular, the second device 15' transfers heat from the water to the air flow to be heated indirectly, that is without direct contact between the water and the air flow.

[0224] In the particular embodiments of figures 6 and 7, the second device 15' is a heat-pipe heat exchanger.

[0225] For the sake of description brevity, reference shall be made to the generic description of a heat-pipe heat exchanger outlined above.

[0226] In the embodiment of figures 6 and 7, the second device 15 is configured to cover a percentage comprised between 50% and 90% of the average load of the second burner 13' so as to allow the second device 15' to provide a constant thermal power and at the same time rapidly meet the sudden thermal power changes required by the second burner 13'.

[0227] Therefore, the second recirculation duct 16', also comprises a fourth temperature sensor 33', positioned downstream of the second device 15' and upstream of the second burner 13' so as to control the temperature of the air flowing out from the second device 15' and, therefore, the percentage of the average load of the second burner 13' covered by the second device 15'.

[0228] In particular, as shown in figures 6 and 7, the monitoring and control unit UMC is operatively connected to the fourth temperature sensor 33' and to the second pumping system 29' so as to control the water flow rate depending on the temperature detected by the fourth temperature sensor 33' and by the third temperature sensor 35', as described above with reference to the first recirculation duct 16.

[0229] In a variant embodiment, not shown, the second recirculation duct 16' comprises a second bypass sub-duct as described above with reference to the first recirculation duct 16.

[0230] Now, with reference to figure 8, herein described is a non-limiting embodiment of a plant 100 for manufacturing ceramic tiles according to the invention.

[0231] The plant 100 comprises (i) a ceramic pressing station S0, at which a ceramic powder is compacted to form a green ceramic substrate SC, (ii) a drying station, at which the green ceramic substrate SC is dried, (iii) a decoration station, at which an exposed surface of the dried green ceramic substrate SC is decorated and (iv) a firing station S3, at which the decorated ceramic substrates SC are fired.

[0232] In particular, the drying station (S1) comprises a system (10) as described above.

[0233] The plant for manufacturing ceramic tiles further comprises transport means 80 configured to transport the ceramic substrates SC from one station to the subsequent one along an advancement direction DA.

[0234] In the particular embodiment described herein, the transport means 80 comprise a conveyor belt movable along the aforementioned advancement direction DA.

[0235] In the particular embodiment described herein, the pressing station S0 comprises a pressing machine 50 adapted to compact a ceramic powder obtained from the grinding and atomisation of ceramic raw materials (which varies in terms of quantity and type depending on the desired composition of the green ceramic substrate) and therefore define the format of the green ceramic substrate SC.

[0236] In the particular embodiment described herein, the decoration station S1 comprises: a first airbrush 60 provided with a plurality of airless nozzles adapted to evenly deposit a layer of engobe on the exposed surface of the dried ceramic substrate SC so as to adjust the colour tone thereof so as to provide the decoration; a ceramic digital ink jet printer 61 for obtaining the decoration; a second airbrush 62 provided with a plurality of airless nozzles adapted to deposit a of glaze protection layer on the decorated exposed surface.

[0237] In particular, the firing station S3 comprises a ceramic kiln 70.

[0238] By way of non-limiting example, the ceramic kiln 70 is a roller ceramic kiln configured to fire the ceramic substrates SC at maximum temperatures which can reach 1250-1300°C (firing temperature of the porcelain stoneware ceramic tiles).

[0239] In detail, the first source S1 and / or the second source S2 comprises a heat exchange equipment configured to transfer heat from the combustion fumes, and / or the air for cooling the tiles, of the ceramic kiln 70 of the plant 100 to the first heat carrier fluid and / or second heat carrier fluid respectively circulating in the first heating circuit CR1 and of the second heating circuit CR2.

[0240] The heat exchange equipment may comprise a heat-pipe heat exchanger configured to transfer heat from the combustion fumes of the ceramic kiln 70 of the plant 100 to the first heat carrier fluid and / or second heat carrier fluid.

[0241] For the sake of description brevity, reference shall be made to the description above of a heat-pipe heat exchanger.

[0242] Alternatively, the heat exchange equipment may comprise a finned pack exchanger configured to transfer heat from the air for cooling the tiles of the kiln 70 of the plant 100 to the first heat carrier fluid and / or second heat carrier fluid.

[0243] Also in this case, for the sake of description brevity, reference shall be made to the description above of a finned pack exchanger.

[0244] In the light of the above, it is clear that the drying system 10 and the plant 100 for manufacturing ceramic tiles attain all the set objects overcoming the drawbacks of the prior art.

[0245] As a matter of fact, the invention allows to reduce the environmental impact of the ceramic industry.

[0246] In particular, the system 10 has a low consumption of gaseous fuel.

[0247] Even in greater detail, during the experimentation, it was estimated that in the event of a system 10 according to the embodiment of figures 1 and 2, the consumption of gaseous fuel is reduced up to approximately 50%.

[0248] On the other hand, the decreased consumption of gaseous fuel may be decreased up to approximately 75% in the event of a system 10 according to the embodiments of figures 6 and 7.

[0249] Clearly, also the plant 100 for manufacturing ceramic tiles thus obtained has low consumption of gaseous fuel.

[0250] Even more particularly, it should be observed that in the event that the first source S1 and / or the second source S2 comprises a heat exchange equipment configured to transfer heat from the combustion fumes, and / or of the air for cooling tiles, of the ceramic kiln to the first heat carrier fluid and / or second heat carrier fluid, the decrease in consumption of gaseous fuel does not entail significant operating costs given that there is exploited the heat of the exhaust fumes of the ceramic kiln, and / or of the air for cooling the tiles, which, would otherwise be dispersed.

[0251] The description outlined above and shown in the attached drawings may be subjected to variants and / or additions. Basically, the materials - to the extent which they are compatible with the specific use and with the respective individual components they are designed for - may be suitably selected as a function of the required requirements of the current state of the art.

Claims

1. Air drying system (10) for ceramic products, comprising: - a drying chamber (11) in which green ceramic substrates (SC) are dried, and provided with an inlet (19) through which said green ceramic substrates (SC) enter into said chamber (11), and an outlet (20) through which said green ceramic substrates (SC) exit from said chamber (11), - transit means (14) for the controlled passing through of the green ceramic substrates (SC) within said chamber (11), - at least one first recirculation duct (16), connected to said chamber (11) through a first air inlet opening (27) and a first air outlet opening (28) obtained on said chamber (11), and comprising a first fan (12), for the recirculation of air, and a first burner (13), for heating the air, operatively connected, said first recirculation duct (16) further comprising a first heat exchange device (15) adapted to place in flow communication said first fan (12) and said first burner (13), - a first heating circuit (CR1) operatively connected to said first device (15) and provided with a first source (S1) for supplying a first heat carrier fluid, and with a first pumping system (29) for moving said first heat carrier fluid, for indirectly transferring heat from said first heat carrier fluid to the air circulating in said first recirculation duct (16), - a first monitoring and control unit (UMC) adapted to control said first fan (12), said first burner (13) and said transit means (14).

2. System (10) according to claim 1, wherein the section (A1) of said first recirculation duct (16) at said first device (15) is larger than the section (A2) of said first recirculation duct (16) at said first fan (12) and the section (A3) of said first recirculation duct (16) at said first burner (13).

3. System (10) according to claim 1 or 2, wherein said first device (15) is configured to cover a percentage comprised between 50% and 90% of the average load of said first burner (13).

4. System (10) according to any one of the preceding claims, wherein said first recirculation duct (16) comprises a first recirculation sub-duct (30) along which there is positioned a bypass valve (34) for bypassing, if need be, said first device (15) placing in direct flow communication said first fan (12) and said first burner (13), said first recirculation duct (16) further comprising a first exclusion valve (31) and a second exclusion valve (32) respectively positioned between said first fan (12) and said first device (15) and between said first device (15) and said first burner (13), wherein said bypass valve (34) and said exclusion valves (31,32) can be remote controlled by said monitoring and control unit (UMC).

5. System (10) according to any one of the preceding claims further comprising at least one second recirculation duct (16') connected to said chamber (11) by means of a second air inlet opening (27') and a second air outlet opening (28) obtained in said chamber (11), said second recirculation duct (16') comprising at least one second fan (12') and a second burner (13') which are operatively connected and can be controlled by said first monitoring and control unit (UMC).

6. System (10) according to claim 5, wherein said second recirculation duct (16') further comprises a second heat exchange device (15') adapted to place in flow communication said second fan (12') and said second burner (13'), said second device (15') being operatively connected to a second heating circuit (CR2), supplied by said first source (S1) or from a second source (S2) of a heat carrier fluid, for transferring heat from said first heat carrier fluid or from said second heat carrier fluid to the air circulating in said second recirculation duct (16').

7. Plant (100) for producing ceramic tiles comprising in a long order an advancement direction (DA): - a pressing station (S0), at which a ceramic powder is compacted to form green ceramic substrates (SC), - a drying station (S1), at which said green ceramic substrates (SC) are dried, - a decoration station (S2), at which an exposed surface of said dried green ceramic substrates (SC) is decorated, and - a firing station, comprising a ceramic kiln (70), at which said decorated ceramic substrates (SC) are fired, and - transport means (80) configured to transport said ceramic substrates (SC) from one station to the subsequent one along said advancement direction (DA), wherein said drying station (S1) comprises a drying system (10) according to any one of claims 1 to 4.

8. Production plant (100) according to the preceding claim, wherein said first source comprises a heat exchange equipment configured to transfer heat from the combustion fumes and / or from the air for cooling tiles, of said ceramic kiln (70) to said first heat carrier fluid.

9. Plant (100) for producing ceramic tiles comprising in a long order an advancement direction (DA): - a pressing station (S0), at which a ceramic powder is compacted to form green ceramic substrates (SC), - a drying station (S1), at which said green ceramic substrates (SC) are dried, - a decoration station (S2), at which an exposed surface of said dried green ceramic substrates (SC) is decorated, and - a firing station, comprising a ceramic kiln (70), at which said decorated ceramic substrates (SC) are fired, and - transport means (80) configured to transport said ceramic substrates (SC) from one station to the subsequent one along said advancement direction (DA), wherein said drying station (S1) comprises a drying system (10) according to claim 5.

10. Production plant (100) according to the preceding claim, wherein said first and / or said second source comprises a heat exchange equipment configured to transfer heat from the combustion fumes and / or from the air for cooling tiles, of said ceramic kiln (70) to said first heat carrier fluid and / or said second heat carrier fluid.

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