IT202100016352A1 - HEATER GROUP AND INDUSTRIAL APPARATUS FOR THE FIRING OF CERAMIC PRODUCTS - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

?HEATER GROUP AND INDUSTRIAL APPARATUS FOR THE FIRING OF CERAMIC PRODUCTS?

TECHNICAL SECTOR

The present invention ? relating to a heating unit and an apparatus for firing ceramic articles. In particular, the present invention finds advantageous but not exclusive application in the firing of ceramic products to obtain tiles, which the following description will make explicit reference without losing in generality?.

BACKGROUND OF THE INVENTION

The firing of ceramic products to obtain tiles generally takes place in tunnel kilns, delimited by two opposite walls and a roof.

These furnaces are usually heated by two sets of burners, typically operating on methane gas, each arranged on one side of the tunnel. These burners are usually placed on the side walls of the tunnel on several levels. levels and face the opposite wall.

The firing cycle of ceramic artefacts? studied with great precision and provides for: the heating of the ceramic products starting from the entrance to the kiln, their permanence inside the firing chamber at a predefined temperature and controlled cooling before reaching the kiln outlet.

Usually, the ceramic products are transported on a large conveyor made up of a series of ceramic rollers. Consequentially, ? It is important to ensure that the temperature inside the cooking chamber is uniform along the entire width of the oven.

For this purpose, various types of industrial burners have been developed, as well as different dispositions of the burners themselves inside complex apparatuses, to obtain an increasingly higher temperature? constant inside the cooking chamber.

Furthermore, as previously mentioned, known type of ceramic burners are substantially fed with fossil fuels (methane, LPG), which, although they allow on the one hand to reduce NOx emissions through normal combustion, on the other hand they cause an anti-ecological exploitation of non-renewable resources and the emission of CO2 and all other combustion waste products.

To try to overcome these problems, methods have been developed for electric heating of kilns for firing ceramic articles, which provide for the installation in the kiln compartment of heating rods or heating conductors to give off heat and heat it.

However, these methods have some disadvantages. One of the main disadvantages ? linked to? aggression? of the fumes generated by the firing of the ceramic articles, especially in the pre-heating area of the kiln itself, which induce rapid erosion of the heating rods or heating conductors installed in the kiln, thus forcing frequent maintenance or replacement of these heating elements. To try to overcome this problem, these heating bars or heating conductors are generally installed only in the cooking area of the oven, where the fumes produced are not highly aggressive. chemical, while in the pre-heating zone industrial burners of known type are used.

Furthermore, is the electric heating of these kilns for firing ceramic products ? more expensive compared to oil or gas, regardless of whether electricity is whether used from the network or internally. Another drawback of the known methods for electric heating of kilns for firing ceramic articles? linked to the often excessive radiation effect, which does not allow uniform distribution of heat in large combustion chambers.

Another drawback of the known methods for electric heating of kilns for firing ceramic articles? linked to the impossibility? to fire the body of the ceramic article uniformly along its entire section. In particular, with the known methods ? It is possible to fire uniformly along the entire thickness only ceramic articles up to 6 mm thick.

Purpose of the present invention? to provide a heating unit and an industrial apparatus for firing ceramic articles which allow the drawbacks of the known art to be overcome, at least partially, are, at the same time, easy and cheap to manufacture and involve a reduction in CO2 emissions.

SUMMARY

In accordance with the present invention, a heating unit and an industrial apparatus for firing ceramic products are proposed according to what is stated in the attached independent claims, and preferably, in any one of the claims depending directly or indirectly on the mentioned independent claims.

The claims describe preferred embodiments of the present invention forming an integral part of the present description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinafter with reference to the attached drawings, which illustrate some non-limiting embodiments, in which:

figure 1 represents a schematic view in front section of an industrial apparatus for firing ceramic articles in accordance with an embodiment of the present invention;

- figure 2 ? a perspective view of a heater assembly in accordance with an embodiment of the present invention;

- figure 3 ? a front view and in section of the heating unit of figure 2 installed in a kiln for firing ceramic articles;

- figure 4 ? an enlarged view of a portion of the heater assembly of FIG. 3;

- figure 5 ? a graph showing the temperature variation inside the cooking chamber of the oven as a function of the distance from the hot gas injection point inside the cooking chamber itself (the distance is shown on the abscissa, the temperature on the ordinate); And

- figure 6 ? a graph that shows the variation of the speed? hot gas outlet inside a cooking chamber of an oven as a function of the distance from the hot gas entry point inside a cooking chamber itself (the distance is shown on the abscissa, the temperature on the ordinate) .

DETAILED DESCRIPTION

In the attached figures, with 1 ? indicated as a whole a heating unit for firing ceramic articles T in accordance with a first aspect of the present invention.

In detail, in the present discussion by ceramic articles T we mean any type of article made of ceramic material which requires at least one firing in an industrial kiln 2 (such as the one partially illustrated in figure 1), for example ceramic slabs or tiles.

Heater group 1 ? installable in an industrial oven 2, in particular in a tunnel oven 2, comprising a cooking chamber 3.

In particular, as shown schematically in figure 1, advantageously but not in a limiting manner, during firing, the ceramic articles T are moved by a transport system 4 along a conveying path P (shown schematically in figure 1 and which extends orthogonally to the plane visible in figure 1).

According to some advantageous but non-limiting embodiments, the conveying system 4 comprises a series of rollers arranged in succession along a direction parallel to the conveying path P, on which the raw ceramic articles T to be fired are arranged, preferably in an orderly manner. .

In detail, advantageously but not limitingly, the transport system 4 comprises a plurality of of ceramic rollers (possibly also moving at different speeds to differentiate the firing of the manufactured articles) arranged in succession along the conveying path P (i.e. along the direction parallel to the conveying path P) so as to define a conveying plane intended to receive the ceramic products T and move them along the conveying path P.

With particular reference to figures 2 and 3, advantageously but not limitingly, the heater group 1 comprises an electric heater 5, comprising, in turn, a tubular casing 6 having at one end 7 a supply duct 8 for supplying a gas G (schematically illustrated with arrows in figure 3) inside the tubular casing 6 and at least one electric heating element (not shown in the attached figures) which extends inside the? tubular casing 6 and ? which can be activated to heat, by the Joule effect, the gas G.

In detail, advantageously, the gas G comprises (in particular, consists of) ambient air having, for example, at least 21% oxygen.

Advantageously but not limitingly, the electric heater 5 also comprises at least one support (not visible in the attached figures) fixed internally to the tubular casing 6 and configured to support at least the electric heating element so as to keep it stationary with respect to the tubular casing 6.

This arrangement of the electric heating element inside the casing 6 protects the electric heating element from the chemical aggression of any fumes and/or waste gases coming from the cooking chamber 3, increasing the useful life of the heating unit 1 with respect to the electric heating units known for firing ceramic articles T.

According to some advantageous but not exclusive embodiments, the aforementioned support comprises (in particular, it is formed by) a rod; even more advantageously a plurality? auctions arranged to define among them a plurality? of hollow channels. Advantageously but not limitingly (in this case), the electric heating element comprises (in particular it is formed by) an electric wire, for example a Kanthal wire, wound around each/such rod and configured to heat the gas G by the Joule effect which passes through the tubular casing 6. According to alternative embodiments, the support element comprises a plurality of of perforated spacers (not visible in the attached figures) which extend radially with respect to the tubular casing 6 and follow one another along a longitudinal axis X of the tubular casing 6 itself so as to define a plurality of longitudinal channels open at least at the ends?.

Furthermore, advantageously but not limitingly, the electric heating element comprises (in particular, it is formed by) an electric wire, for example a Kanthal wire, which extends through the holes, for example wound in a helix in the various adjacent holes, and configured to heat the gas G which passes through the tubular casing 6 by means of the Joule effect.

According to some advantageous but non-limiting embodiments, the electric heater 5 also comprises an insulating layer (not visible in the enclosed figures) arranged at one end of the 9 of the tubular casing 6, opposite the end? 7, and provided with an opening (not visible in the attached figures) configured to allow the gas G to escape from the tubular casing 6. Advantageously but not restrictively, this opening? configured to place the electric heater 5 in fluid communication with a tubular exhaust element 10, which will be? better described below.

Advantageously but not limitingly (according to some embodiments not shown) the heater unit 1, in particular the electric heater 5 further comprises at least one temperature control device (not shown) and advantageously comprising at least one thermocouple for detecting the temperature ( gas G) inside the electric heater 5. Alternatively or in combination, the heater group 1, in particular the electric heater 5 further comprises at least one unit? control (not shown) to control (in a known way), possibly according to the data detected by the temperature control device, the operation of the electric heater 5.

According to some advantageous but non-limiting embodiments, the electric heater 5 is a commercially known product and described in one of the following patent documents WO2020193479, EP3721150 and EP3721149.

Advantageously but not limitingly, the heater unit 1 also comprises a tubular exhaust element 10 which extends from the tubular casing 6 of the electric heater 5, on the opposite side with respect to the adduction duct 8 (in particular, which extends from the 9 end of the electric heater 5) and ? configured to receive and to be crossed by the gas G at the outlet of the electric heater 5 and comprises at least one intake outlet 11 for introducing at least part of the aforementioned gas G towards the outside of the tubular exhaust element 10 .

Advantageously but not limitingly, this inlet outlet 11 has a through hole with an equivalent diameter of less than or equal to about 25 mm. Pi? advantageously but not limitingly, the through hole of the inlet outlet 11 has an equivalent diameter less than or equal to about 20 mm; especially less than or equal to about 15mm. even more advantageously, the one through hole of the at least one input outlet 11 ? greater than or equal to about 15mm, especially about 10mm.

It should be noted that in the present text, by equivalent diameter of a through hole we mean the diameter of a circle having the same area as the through hole.

In use, this sizing of? output 11 allows you to increase the speed? with which the aforementioned gas G, once heated, is introduced out of the tubular exhaust element 10, resulting in a greater linearization of the gas flow G. Furthermore, this dimensioning causes an increase in the turbulent motions inside the exhaust element 10 tubular with consequent facilitation of the heat exchange between the electric heating element and the gas G.

Advantageously but not necessarily (as illustrated in figures 2 and 3), the tubular discharge element 10 comprises an end portion 12 coupled to a part 13 of the tubular casing 6 and an end portion 14 opposite the end portion 12?.

Advantageously but not in a limiting way (as illustrated in the non-limiting embodiment of figures 2 and 3), the output 11 is disposed at the end portion 14?.

Pi? precisely, the?exit 11 of entry ? arranged along the axis X of longitudinal symmetry of the tubular discharge element 10; more advantageously the through hole of the input outlet 11 ? arranged along the X axis of longitudinal symmetry; even more advantageously this through hole of the input outlet 11 ? centered with respect to the X axis, i.e. of longitudinal symmetry of the tubular discharge element 11.

Advantageously but not limitingly (as in the illustrated embodiment), the tubular discharge element 10 and is substantially coaxial to the tubular casing 6. In detail, the tubular discharge element 10 comprises a longitudinal axis of symmetry X, which advantageously but not limitingly coincides with (ie lies on the same straight line as) the axis X of longitudinal symmetry of the casing tubular 6.

Advantageously but not limitingly, the end portion 12? of the tubular 11 exhaust element? configured to couple with the part 13 of the tubular casing 6; in particular according to some non-limiting embodiments (such as the one shown in figure 3) the end portion 12? ? configured to externally wrap the part 13 of the tubular casing 6 so as to place the tubular casing 6 of the electric heater 5 in fluid communication with the tubular discharge element 10 so that the gas G described above can pass inside the tubular discharge element 10; in other words, the tubular casing 6 is inserted into the tubular discharge element 10 at this end portion 12.

Advantageously but not necessarily, the tubular discharge element 10 has a circular cross-section, in particular with a constant diameter. Furthermore, advantageously but not necessarily, the tubular discharge element 10 is made in one piece, especially in silicon carbide.

Advantageously but not necessarily, (also) the tubular casing 6 has a circular cross-section, in particular with a constant diameter.

According to some advantageous but non-limiting embodiments (see for example figure 3), the tubular discharge element 10 comprises a main hollow portion 17 which extends, advantageously but not necessarily without solution of continuity, from the portion 12 of end? to the portion 14 of the end? and ? configured to receive and to be crossed by gas G leaving the electric heater 5.

According to some advantageous but non-limiting embodiments, the end portion 14? comprises (in particular, defines) a taper 18 configured to guide the gas G from the hollow main portion 17 to the inlet outlet 11 (see figures 3 and 4).

The presence of the tapering 18 increases the speed? of the gas G leaving the tubular exhaust element 10, in particular from the exit 11, causing a further increase in the turbulent motions inside the tubular exhaust element 10 and thus facilitating the heat exchange between the electric heating element and the gas G. Furthermore, this tapering 18 involves a loss of head, and therefore of flow rate, of the gas G which induces a further advantageous increase in the temperature of the gas G for the same temperature. of heat produced by the Joule effect from the electric heater 5.

According to some advantageous but non-limiting embodiments (such as the one illustrated in the attached figures), the heating unit 1 also comprises: a hollow body 20 which is? coupled to the tubular discharge element 10 and ? intended to be crossed by (at least part) of the gas G at the outlet of the tubular exhaust element 10 (through the introduction outlet 11); a suction element 21, which ? disposed between the tubular discharge element 10 and the hollow body 20, ? equipped with one or more openings 22 and ? configured to carry, in use, at least part of the waste gases F present outside the heating unit 1 (in particular, inside the cooking chamber 3) into the hollow body 20; and an?exit 11?? introduction to introduce at least part of the gas G towards the outside of the hollow body 20 (in particular, towards the outside of the heating unit 1; even more particularly, in use, towards the cooking chamber 3 of the oven 2).

Advantageously but not restrictively, this output 11?? has a through hole with an equivalent diameter less than or equal to approximately 60 mm.

Furthermore, advantageously but not in limitation, exit 11?? of entry ? arranged on the hollow body 20 (in particular, in use - ie when the heating unit 1 is mounted in the oven 2 - facing the inside of the cooking chamber 3).

even more precisely, advantageously but not limitingly, the hollow body 20 comprises an end portion 19 and exit 11?? of entry ? arranged in correspondence with this end portion 19? of the hollow body 20 along the axis X of longitudinal symmetry of the tubular discharge element 10.

Advantageously in this case, the tubular discharge element 10 is arranged between the electric heater 5 and the suction element 21.

According to some non-limiting embodiments such as the one illustrated in figure 3, advantageously but not necessarily, in use, the hollow body 20 is located (completely) entirely inside the cooking chamber 3.

Advantageously but not limitingly, the suction element 21 is configured to create a vacuum between the tubular discharge element 10 and the hollow body 20 so as to carry, in use, at least part of the waste gases F present in the cooking chamber 3 into the hollow body 20. The introduction of waste gases F already? hot gases which join the aforementioned gas G inside the tubular exhaust element 10, favors the heating of the gas G and increases its turbulence.

Advantageously but not limitingly, the openings 22 extend through the suction element 21 (for example, they have an elongated shape and are arranged longitudinally to the tubular discharge element 10 and to the hollow body 20).

According to some non-limiting embodiments (such as the one illustrated in the attached figures), the tubular discharge element 10 is substantially coaxial with the hollow body 20. In other words, the longitudinal symmetry axis X of the tubular discharge element 10 coincides with the longitudinal symmetry axis X of the tubular discharge element 10 and of the hollow body 20.

According to some non-limiting embodiments, the suction element 21 comprises, in particular 2, a Venturi tube.

Furthermore, according to some non-limiting embodiments (such as the one illustrated in Figure 4), the suction element 21 has a bottleneck 23. Furthermore, the suction element 21 has a section 24 with a frustoconical shape, delimited by a larger base 25 and a minor base 26. Pi? in particular, advantageously but not necessarily, the minor base 26 coincides with the aforementioned bottleneck 23; the major base 25 ? coupled to the second hollow body 20. Advantageously but not necessarily, the openings 22 are made on the truncated-conical section 24 of the suction element 21. In particular, they cross the section 24 of the suction element 21 from side to side (transversally).

Advantageously but not necessarily (and as illustrated in figures 2, 3 and 4), the suction element 21 (also) comprises reinforcing ribs 27. Thanks to these ribs 27, ? It is possible to lengthen the hollow body 20 as desired without risking that the tubular discharge element 10 so fact it breaks in correspondence with the section with the smallest section, i.e. in correspondence with the suction element 21.

Advantageously but not necessarily, the tubular discharge element 10 has a circular cross-section, in particular with a constant diameter.

Advantageously but not necessarily, the hollow body 20 has a circular cross-section, in particular with a constant diameter.

Advantageously but not necessarily, the suction element 21 has a circular cross section.

even more advantageously but not necessarily, the suction element 21 has a circular cross-section with a substantially variable diameter.

Advantageously but not necessarily, the bottleneck 23, i.e. the cross section TT (FIG. 4) of the bottleneck 23 has a diameter smaller than two-thirds of the diameter of the hollow body 19 and the hollow body 20. Pi? in particular, the transversal section TT (figure 4) of the bottleneck 23 has a diameter of less than half the diameter. of the diameter of the tubular discharge element 10 and of the hollow body 20.

Pi? in particular, Advantageously but not necessarily, the bottleneck 23, ie the transversal section TT (figure 4) of the bottleneck 23 has a diameter smaller than one third of the diameter of the hollow body 19 and of the hollow body 20. In particular, the transversal section TT of the bottleneck 23 has a diameter greater than one sixth of the diameter of the diameter of the tubular discharge element 10 and of the hollow body 20.

even more advantageously but not limitingly, the narrowing 23, ie the transversal section TT (figure 4) of the narrowing 23, has a diameter smaller than one third of the diameter of the tubular discharge element 10 and of the second hollow body 20.

In particular, in this case, advantageously but not limitingly, the bottleneck 23 (or the transversal section TT (figure 4) of the bottleneck 23) has a diameter ranging from about 10 mm (in particular from about 20 mm; more particularly from about 25 mm) to about 60 mm (in particular about 40 mm; more particularly about 35 mm. Advantageously but not limitingly, the tubular discharge element 10 and the hollow body 20 have a diameter between about 30 mm (specifically, about 40 mm; more specifically, about 50 mm) and about 200 mm (specifically, about 120 mm; more specifically, about 100 mm).

Pi? the diameter of the bottleneck 23 decreases, with respect to the diameter of the tubular discharge element 10, more? the variation of the speed? with which the gas G s moves inside the tubular exhaust element 10 increases. The increase in speed? ? advantageous both because? allows you to let out the gas G with greater speed?, both because? it increases the turbulence of the gas G inside the heating unit 1, advantageously improving the heat exchange between the gas and the electric heating element.

In the non-limiting embodiment illustrated in figures 2 to 4, the tubular discharge element 10, the hollow body 20, and the suction element 21 form a single body, even more? advantageously they are made in one piece, in particular in silicon carbide.

In particular, a lateral surface 28 of the tubular discharge element 10, of the hollow body 20 and of the suction element 21 ? (at least) partially seamless. Pi? in particular, the lateral surface 28 ? seamless? in the sections not interrupted by the openings 22 (see figures 2 and 3).

Advantageously but not necessarily, this single body (which comprises the tubular discharge element 10, the hollow body 20, and the suction element 21) is made in one piece, especially in silicon carbide.

Alternatively, advantageously but not necessarily, this single body (which comprises the tubular discharge element 10, the hollow body 20 and the suction element 21) is made by additive manufacturing, in particular 3D printing.

According to yet other non-limiting and not illustrated embodiments, this single body (which comprises the tubular discharge element 10, the hollow body 20 and the suction element 21) is formed by welding the various constituent elements, namely, in this case, the tubular discharge element 10, the hollow body 20, and the suction element 21.

According to other non-limiting and not illustrated embodiments, this single body (which comprises the tubular discharge element 10, the hollow body 20 and the suction element 21) is formed through the mechanical coupling with fastening systems (e.g. bolts, screws, rivets, etc.) of the various constituent elements, i.e., in this case, of the tubular discharge element 10, of the hollow body 20, and of the ?suction element 21.

According to further non-limiting embodiments, this single body (which includes the tubular discharge element 10, the hollow body 20 and the suction element 21) is formed using mold casting techniques.

According to some embodiments not shown, the heating group 1 comprises a plurality of hollow bodies (similar to the hollow body 20) spaced between them by corresponding suction elements (of the type of suction element 21).

According to some embodiments not shown, the heater group 1 comprises a high-head fan to feed gas G (comprising, in particular, it consists of ambient air having at least 21% oxygen) to the electric heater 5. advantageously allows to compensate at least part of the head losses, and therefore of the flow rate, of the gas G which arise while the gas G passes through the tubular casing 6 and the discharge element 10, preserving its flow rate.

With particular reference to figure 1, according to another aspect of the present invention, an industrial apparatus for firing ceramic articles T is proposed, indicated as a whole by the numeral 29.

The industrial apparatus 29 comprises an oven 2 (as described above), in particular a tunnel oven, provided with at least one side wall 30 and a roof or vault 31 which delimit a cooking chamber 3 which has a surface 32 inside the chamber 3 cooking chamber and a surface 33 outside the cooking chamber 3.

In particular, oven 2 ? advantageously as a tunnel it has two walls 30? and 30?? opposing sides which form the side wall 30, between which the ceramic products T and a roof 31 pass.

The industrial apparatus 29 also comprises a transport system 4 (like the one described above), in particular horizontal, which (as mentioned above) is fit to move a plurality? of ceramic articles T along a conveyance path P inside the firing chamber 3 (from an inlet to an outlet of the firing chamber 3).

The transport system 4 can? be any type of transport system.

Advantageously (as mentioned above), the transport system 4 comprises a series of rollers made of refractory material, on which the unfired ceramic articles T to be fired are arranged, preferably in an orderly manner. Pi? in detail (according to some advantageous but non-limiting embodiments), the transport system 4 comprises a plurality? of ceramic rollers (possibly moved at different speeds to differentiate the firing of the manufactured articles) which define a conveying plane.

The apparatus 29 also comprises a heating system 34 (partially illustrated in figure 1) configured to heat the cooking chamber 3 so as to cook the plurality of? of ceramic manufactured articles T passing inside said firing chamber 3 and obtaining finished ceramic products, for example ceramic tiles.

Advantageously, the heating system 34 comprises at least one heating group 1. Even more? advantageously, the heating system 34 comprises a plurality of of heating groups 1 arranged in series along a direction parallel to the conveying path P.

even more in detail, with particular reference to figure 1, advantageously, the heater unit 1, in particular each heater unit 1, is made as previously described.

Advantageously but not limitingly, the cooking chamber 3 of the oven 2 comprises (in particular it is divided into) at least one pre-heating zone, a pre-cooking zone, a cooking zone and a cooling zone arranged (one after the other). other) along the conveying path P. Advantageously but not necessarily, the pre-heating area is? connected to the pre-cooking area and to the cooking area (seamlessly), plus? in particular in a direct way (that is to say without the interposition of further zones and/or rooms). Advantageously, the cooking zone and the cooling zone are also, preferably but not necessarily, connected (seamlessly), in particular in a direct way (that is to say without the interposition of further chambers and/or zones) .

In detail, inside the preheating and pre-firing zones, the temperature of the ceramic articles T is gradually raised until it reaches a firing temperature equal to at least about 1100?C, in particular equal to at least about 1200?C, which is kept constant throughout the cooking area; while inside the cooling zone the temperature of the basic ceramic articles BC fired leaving the firing zone 6 is rapidly reduced.

Advantageously but not limitingly, at least a part of the cited heating groups 1? arranged in correspondence with the pre-heating zone (in particular, also in the pre-cooking zone) to heat at least the pre-heating zone of said cooking chamber 3 so as to impose inside said pre-heating zone a temperature of at least about 1000?C, in particular of at least about 1100?C.

Advantageously but not in a limiting way, according to some non-limiting and not illustrated embodiments, the heating system 34 of the apparatus 29 also comprises a plurality of of electric radiant panels arranged inside the cooking chamber 3, in particular they are arranged on the surface 32 of the vault or roof 31 and above the surface of a bottom or sole or floor 35 of the cooking chamber 3 of the oven 2. The function of these radiant panels? that of setting the aforementioned cooking temperature inside the cooking zone itself. In this way, ? Is it possible to produce a fully electric apparatus 29 for firing ceramic products T, the benefit of which is? the substantial reduction of CO2 emissions.

According to some advantageous but non-limiting embodiments, the groups of heaters 1 are arranged (that is, they are mounted on the walls of the oven) on several? levels inside the side wall 30 of the oven 2; in particular of both the aforementioned walls 30?, 30?? sides of the oven 2.

In detail, advantageously, in the case in which the conveying system 4 comprises (is formed by) ceramic rollers as described above, at least a part of the heating units 1 are arranged below the conveying plane. The presence of heating groups 1 also below the conveying surface allows a more? uniform heat distribution inside the cooking chamber 3.

In combination (as illustrated in the non-limiting embodiment illustrated in Figure 1) or alternatively, at least part of the heating units 1? arranged in correspondence with the roof or vault 31 of the furnace 2. In detail, advantageously but not limitingly, the/each heating unit 1 arranged on the roof or vault 31 is installed inclined with respect to the vertical and/or with respect to the path P for conveying the ceramic articles, in particular at an angle which varies between approximately 0? and about 60? about X and about Y with respect to the vertical and/or an angle varying between about 0? and about 60? with respect to the conveying path P.

Advantageously, the heating units 1 are arranged (that is mounted) on the furnace 2 oriented in a transversal direction (in particular, perpendicular) to the direction A of advancement (and therefore to the conveying path P).

The counter-current arrangement (that is, orthogonal to the advancement direction of the ceramic articles T) of the heating groups 1 allows to avoid the risk that the gas jet G leaving the heating group 1 arrives directly on the ceramic articles T, with consequent risk of damage to them.

Advantageously but not necessarily, the/each heating group 1 ? arranged (ie installed) in such a way that at least part of the tubular discharge element 10 protrudes at least partially inside the cooking chamber 3.

even more in detail according to some advantageous but non-limiting embodiments, the tubular discharge element 10 of (or of each) heating unit 1 has a length of at least about 900mm and the heating unit 1? installed so that the discharge element 10 protrudes inside the cooking chamber 3 for a length of at least about 600mm.

According to yet other advantageous but non-limiting embodiments such as the one illustrated in figures 2, 3 and 4, the tubular discharge element 10 is configured (in particular ? dimensioned) so as to pass transversely through the cooking chamber 3 oriented so that the outlets 11, 11? above described are oriented towards the central part of the cooking chamber 3. even more in particular, in this case, the heater group 1 ? installed so that the tubular discharge element 10 can protrude (i.e. come out) from a first side of said lateral wall 30 (in particular, from wall 30), extend through said cooking chamber 3 to a second side, opposite the first side (particularly up to wall 30?). Advantageously, in this case, the tubular discharge element 10, in particular, its end portion 14? it passes through the entire cooking chamber 3 and fits into the side wall 30?.

Advantageously but not limitingly, the/each heating group 1 ? arranged (i.e. installed) so that the electric heater of (in particular, of each) heater group 1 extends at least partially (in particular, totally) through the (in particular, transversely) side wall or roof or vault 31 of the furnace 2 or la between the inner surface and the outer surface of the cooking chamber 3.

In accordance with some advantageous but non-limiting embodiments (for example the one illustrated in figures 2 to 4), the heating group 1 is installed so that the suction element 21 is arranged, at least partially, inside the cooking chamber 3.

Alternatively or in combination, advantageously but not restrictively, the heating unit 1 is installed so that the electric heater 5 extends at least partially (in particular, totally) across (in particular, transversely) the side wall 30 or the roof or vault 31 of the furnace 2 between the inner surface 32 and the outer surface 33; the tubular discharge element 10 extends at least partially (in particular, totally) through (in particular, transversely) the side wall 30 or the roof or vault 31 of the furnace 2 between the internal surface 32 and the external surface 33; and the hollow body 20 extends substantially completely inside the cooking chamber 3.

According to some non-limiting and not illustrated embodiments, advantageously but not necessarily, the heating unit 1 is installed so that the tubular discharge element 10 protrudes at least partially inside the cooking chamber 3.

In the graph in figure 5, ? illustrated the trend of the temperature according to the distance from the exit 11 or 11?? of the heating group 1; such a graph? been obtained experimentally. In particular, the ordinate axis indicates the temperature inside the cooking chamber 3 and the abscissa axis the distance from the outlet 11 or 11?? of inlet of the heating unit 1, coinciding with the side wall of the oven 2. In detail, the temperature variation indicated with the line I refers to an apparatus 29 with burners of known type, while the temperature variation indicated with the lines II and III refer to an apparatus 29 with heater units 1 both having an electric heater 5 of the type described above but a tubular discharge element 10 with an outlet 11 having a through hole with equivalent diameter (increasing from line II to line III but) greater than about 25 mm, the line V refers to a heater group 1 with a tubular exhaust element 10 with an outlet 11 having a through hole with an equivalent diameter of about 25 mm while the temperature variation indicated with the line IV refers to an apparatus 29 and to a heating unit 1 made according to the present invention . It is therefore evident that, by using an apparatus 29 and a heating group 1 in accordance with the present invention, temperature values are obtained which are lower? similar to those of the known apparatuses equipped with gas burners within a certain distance from the walls 32 of the oven 2, increasing the temperature and the speed? of the gas G outgoing from the heater group 1 and therefore inducing a heating more? uniformity of the cooking chamber 3.

In Figure 6, lines I and II refer to appliances with burners of the known type, lines III and IV refer to appliances with heater groups 1 both having an electric heater 5 of the type described above but a tubular exhaust element 10 with an outlet 11 having a through hole with an equivalent diameter (increasing passing from line III to line IV but) greater than about 25mm, line VI refers to a heating unit 1 with a tubular exhaust element 10 with an outlet 11 having a through hole with an equivalent diameter of about 25 mm, while the line V refers to an apparatus 29 and to a heating unit 1 made according to an embodiment of the invention. This figure illustrates the trend of the speed? of the flame (for lines I and II) or hot gas G (for lines III, IV and V) inside the cooking chamber 3 according to the distance from the outlets 11 and 11?? of the heating unit 1 coinciding with the side wall of the oven 2.

Even this graph? been obtained experimentally. Also from this it can be deduced that by using an apparatus 29 and a heating unit 1 in accordance with the present invention, an increase in the back pressure of the gases G is obtained by increasing their temperature and speed. of exit of the gas G, which becomes pi? similar to that produced by an?architecture already? note in the literature with gas burner at high speed? (curves I and II). Furthermore, from the graph of figure 6 it can be seen that the presence of the suction element 21 favors a sudden increase in speed? favoring its conservation towards the center of the cooking chamber 3 of the oven 2. The position of the suction element 21 ? variable and non-binding according to need? and favors a consequent increase in the turbulence in the cooking chamber 3.

Bench? the invention described above makes particular reference to some very specific embodiments, it is not? to be considered limited to this example of embodiment, all those variants, modifications or simplifications covered by the attached claims falling within its scope, such as for example a different geometry of the tubular discharge element 10 and/or of the outlets 11, 11?? of the intake element 21, a different arrangement of the heating units 1 inside the apparatus 29 (both in terms of position and alignment), a different transport system 4, etc.

The apparatus 29 and the heating unit 1 described above have numerous advantages.

The main advantage of the apparatus 29 and of the heating unit 1 of the present invention lies in the reduction of CO2 emissions and of the consumption of non-renewable raw materials, with consequent evident advantages in environmental terms.

Furthermore, the use of an electric heater 5 such as the one described above allows for more accurate control. precise of the temperatures inside the cooking chamber 3 at least in correspondence with the area which has the heating groups 1 described above, as well as an increase in safety due to the at least partial overcoming of all the drawbacks in terms of safety linked to combustion.

Compared to the known methods and systems for electric heating of kilns for firing ceramic articles, the heater group 1 of the invention allows heating more quickly. effective and uniform the ceramic products T along their entire section. There? allows optimal firing of ceramic articles having dimensions in particular thickness up to about 15 mm, in particular up to about 10 mm.

Furthermore, with the heating unit 1 and with the apparatus 29 of the invention the arising inside the cooking chamber 3 of fumes is limited and therefore the risk of particulate deposit on the ceramic articles T is reduced, with consequent reduction of the risk of damage to the artifacts themselves.

In addition, the heating unit 1 of the present invention, given the geometry and the penetration into the cooking chamber 3, can easily be installed in place of (a standard architecture of the oven 2.

Claims (15)

1. Heating unit (1) for firing ceramic articles (T) which can be installed in an industrial kiln (2) comprising a firing chamber (3); the heater group (1) includes: an electric heater (5), comprising, in turn, a tubular casing (6) having at one end? (7) a supply duct (8) for supplying a gas (G) comprising (in particular, formed by) ambient air inside the tubular casing (6), at least one electric heating element which extends inside the ?tubular casing (6) and ? operable to heat said gas (G); and a tubular discharge element (10) which extends from said tubular casing (6) on the opposite side with respect to said supply duct (8) and ? configured to receive and to be crossed by said gas (G) at the outlet of said electric heater (5); a hollow body (20), which ? coupled to said tubular discharge element (10) and ? intended to be crossed by at least part of said gas (G) leaving said tubular exhaust element (10); a suction element (21), which ? arranged between said tubular discharge element (10) and the hollow body (20), ? equipped with one or more openings (22) and ? configured to carry, in use, at least part of the waste gases (F) present outside said heating unit (1) (in particular, inside the cooking chamber (3)) into the hollow body (20); and an inlet outlet (11??) for introducing at least part of said gas (G) towards the outside of the hollow body (20) (in particular, towards the outside of said heating unit (1); even more particularly , in use, towards said cooking chamber (3) of said oven (2)). 2. Heater unit (1) according to claim 1, wherein: the tubular exhaust element (10) comprises a first end portion (12) with a central heating element (1). coupled to a part (13) of said tubular casing (6), a second end portion (14) opposite to the first portion (12) of the end? coupled to said hollow body (20), and a further inlet outlet (11) arranged in correspondence with said second end portion (14)? along an axis (X) of longitudinal symmetry of said tubular discharge element (10) to put said tubular discharge element (10) and said hollow body (20) into fluid communication; and the hollow body (20) comprises an end portion (19); and the said input output (11??) ? arranged at said end portion (19)? along said axis (X) of longitudinal symmetry of the tubular discharge element (10). The heater assembly (1) according to claim 1 or 2, wherein the inlet outlet (11??) has a through hole with an equivalent diameter less than or equal to about 60 mm; in particular, said further inlet outlet (11) has an equivalent diameter of less than about 25mm. 4. Heating unit (1) according to any one of the preceding claims, wherein the suction element (21) is? configured to create a vacuum between the tubular exhaust element (10) and the second hollow body (20) so as to carry, in use, at least part of the waste gases (F) present in the cooking chamber (3) into the body (20) cable; and said openings (22) extend through the suction element (21) (for example, they have an elongated shape and are arranged longitudinally to the tubular discharge element (10) and to the second hollow body (20). 5. Heating assembly (1) according to any one of the preceding claims, wherein the tubular exhaust element (10) is? coaxial to said hollow body (20) and the suction element (21) comprises a Venturi tube. 6. Heating unit (1) according to any one of the preceding claims, wherein: the suction element (21) has a narrowing (23) and a section (24) of truncated cone shape, delimited by a major base (25) and a minor base (26); the smaller base of said section (24) having a truncated cone shape coincides with said bottleneck (23); the major base (25) of said section (24) having a truncated cone shape? coupled to said hollow body (20); in particular the suction element (21) comprising reinforcing ribs (27). 7. Heating unit (1) according to claim 6, wherein the throat (23) has a diameter smaller than one third of the diameter of the tubular exhaust element (10) and of the second hollow body (20); in particular, the bottleneck (23) has a diameter ranging from about 10 mm (in particular, from about 20 mm; more particularly, from about 25 mm) to about 60 mm (in particular, about 40 mm; more ? specifically, at about 35 mm). The heater unit (1) according to claim 6 or 7, wherein the tubular exhaust element (10) and the second hollow body (20) have a diameter between about 30 mm (in particular, about 40 mm; is specifically, about 50 mm) and about 200 mm (specifically, about 120 mm; more specifically, about 100 mm). 9. Industrial apparatus (29) for firing ceramic articles (T) comprising: a tunnel kiln (2) provided with at least one side wall (30) and a roof/vault (31) which at least partially delimit a chamber (3 ) cooking surface which has an internal surface (32) and an external surface (33); a transport system (4) configured to handle a plurality? of ceramic articles (T) along a conveying path (P) inside the firing chamber (3); and a heating system (34) configured to heat said cooking chamber (3) so as to cook the plurality of? of ceramic products (T) passing inside said firing chamber (3) and obtaining ceramic products (PC); the oven (2) being characterized in that said heating system (34) comprises at least one heating unit (1) according to any one of the preceding claims. 10. Industrial apparatus (29) according to claim 9, wherein said heater group (1) is installed so that said suction element (21) is, at least partially, inside the cooking chamber (3). 11. Industrial apparatus (29) according to claim 9 or 10, wherein the said (in particular, of each) heater group (1) ? installed so that said electric heater (5) extends at least partially (in particular, totally) through (in particular, transversely) the side wall (30) or the roof/vault (31) of the furnace (2) between said inner surface (32) and said outer surface (33); said tubular discharge element (10) extends at least partially (in particular, totally) through (in particular, transversely) the side wall (30) or the roof/vault (31) of the furnace (2) between said inner surface (32) and said outer surface (33); and the hollow body (20) extends substantially completely inside the cooking chamber (3). 12. Industrial apparatus (29) according to any one of claims from 9 to 11, wherein said heater unit (1) is installed so that the tubular outlet element (10) protrudes at least partially inside the cooking chamber (3). 13. Industrial apparatus (29) according to any one of claims 9 to 12, wherein: said heating system (34) comprising a plurality of? of heating groups (1) arranged in series along said conveying path (P); a part of the plurality? of said heating groups (1) ? arranged in correspondence with said roof/vault (31) of the furnace (2); and each heater group (1) of said part of the plurality? of heater groups (1) ? installed inclined with respect to the vertical and/or with respect to the conveying path (P), in particular by an angle varying between about 0? and about 60? with respect to the vertical and/or at an angle varying between about 0? and about 60? with respect to the conveying path (P). 14. Industrial apparatus (29) according to claim 13, wherein: said cooking chamber (3) of said oven (2) comprises (in particular, is divided into) at least one pre-heating zone, a pre-heating zone - cooking immediately downstream of the preheating zone along said determined path (P), a cooking zone downstream of the pre-cooking zone along said determined path (P), and at least one cooling zone downstream of the cooking; and the said plurality? of heater groups? arranged at least in correspondence with said preheating zone (in particular, also in said pre-cooking zone) to heat at least said preheating zone of said cooking chamber (3) so as to impose a temperature of at least about 1100? C, especially of at least about 1200?C. 15. Industrial apparatus (29) according to any one of claims from 9 to 14, wherein: said conveying system (4) comprises a series of ceramic rollers arranged in succession along said conveying path (P) so as to define a conveying surface designed to receive said ceramic articles (T) and move them along said conveying path (P); and at least a part of the heating groups (1) are arranged below said conveying plane.