APPARATUS, BURNER AND METHOD FOR FIRING CERAMIC ARTICLES

Abstract

A burner (1) for firing ceramic articles (T) that can be installed in an industrial kiln (2), comprising a mixing body (5), a first tubular discharge element (11) configured to allow the passage of a fluid (F) flowing out of the mixing body (5), at least one second tubular discharge element (18), and a suction element (19) configured to direct at least some of the gases (G, G') present within the firing chamber (3) to the second tubular discharge element (18), and provided with one or more openings (20) arranged between the first (11) and second (18) tubular discharge elements. The mixing body (5) comprises a multi-stage combustion head (10) disposed at least partially within the first tubular discharge element (11).

Description

APPARATUS, BURNER AND METHOD FOR FIRING CERAMIC ARTICLES MA / 11 CROSS REFERENCE TO RELATED APPLICATIONS This patent application claims priority over Italian patent application no. 102020000010738, filed on 12 / 05 / 2020, and Italian patent application no. 102021000000695, filed on 15 / 01 / 2021, the full description of which is incorporated herein by reference. TECHNICAL FIELD OF THE INVENTION The present invention relates to an apparatus and a burner for firing ceramic articles. In particular, the present invention is advantageously, but not exclusively, applicable to firing ceramic articles to obtain tiles, to which the following description will refer explicitly without loss of generality. BACKGROUND OF THE INVENTION The firing of ceramic items to obtain tiles is generally carried out in tunnel kilns, delimited by two opposite walls and a roof. These ovens are usually heated by two sets of burners, each arranged on one side of the tunnel. Typically, methane gas-operated burners are located on the side walls of the tunnel at various levels, and oriented towards the opposite wall. The firing cycle of ceramic items is designed with great precision and involves: heating the ceramic items at the entrance of the kiln, the residence of the items within the firing chamber at a predefined temperature, and controlled cooling, before reaching the exit of the kiln. Ceramic items are usually transported on a large conveyor belt consisting of a set of ceramic rollers. Therefore, it is important to ensure that the temperature inside the firing chamber is uniform across the entire width of the kiln. For this purpose, different types of industrial burners have been developed, and different arrangements of the burners within the complex apparatus, to obtain a progressively constant temperature within the cooking chamber. However, especially in very wide tunnel kilns, non-uniform temperature distribution generally occurs in different longitudinal sections, with local temperature peaks. MA / 11 determined according to the position of the burners. In particular, in many cases, the temperatures are higher in the center of the tunnel, and lower near the side walls. This uneven temperature inevitably results in firing defects in ceramic items that move near the tunnel walls. Specifically, these defects can be dimensional or morphological, such as a lack of flatness. This leads to an increased number of discarded items. Usually, this temperature difference between the center of the oven and the areas near the side walls is due to the fact that the gases circulating inside the cooking chamber slow down near the walls, reducing the turbulence of the gases and consequently also the heat exchange coefficient. Furthermore, as previously stated, ceramic burners of a known type are supplied substantially with fossil fuels (methane, LPG), which, although on the one hand, allow the reduction in NOx emissions through normal combustion, on the other hand, imply an anti-ecological use of non-renewable resources. MA / 11 MA / 11 Document EP3155320 describes a burner for an industrial furnace, which can be installed in a furnace comprising at least one firing chamber, and which includes a main tubular body provided with at least one first port for the inlet of a fuel, and at least one second port for the inlet of an oxidizer, and with an end nozzle provided with an outlet facing the firing chamber, and elements for activating the combustion of the fuel-oxidizer mixture. The burner further comprises at least one duct, formed between a second tubular element and the furnace wall, adapted to extract a portion of the gases present within the firing chamber and convey them to the outlet of the end nozzle. Document EP1217297 describes a burner for a gas turbine, comprising a conical premixer. The object of the present invention is to provide an apparatus, a burner, and a method that overcome, at least partially, the disadvantages of the known art, and at the same time, are easy and inexpensive to produce. SUMMARY OF THE INVENTION According to the present invention, a burner, apparatus, and method for firing ceramic articles are provided, as claimed in the MA / 11 independent claims following and, preferably, in any of the claims that depend directly or indirectly on the independent claims. The claims describe preferred embodiments of the present invention, which form an integral part of this description. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described with reference to the accompanying drawings, which illustrate some examples of non-limiting embodiments thereof, in which: Figure 1 is a cross-sectional front view of a first embodiment of an apparatus, according to the present invention; Figure 2 is a schematic plan view of a section of a second modality of an apparatus, according to the present invention; Figure 3 is a schematic perspective view of a part of the apparatus of Figure 1, comprising a burner, according to the present invention; Figures 4 and 4a are front section views of two different versions of the part in Figure 3; Figures 5 and 5a are front views in MA / 11 section of two different modalities of a part of the apparatus of Figure 2, comprising an additional burner, according to the present invention; Figures 6 and 6a are schematic perspective views of a part of the burner in Figures 4 and 4a, respectively; Figures 7 and 7a are longitudinal section and detailed views of the burner part of Figures 6 and 6a, respectively; Figures 8 and 8a are cross-sectional front views of a combustion head of the burner of Figures 6 and 6a, respectively; Figures 9 and 10 are two cross-sectional front views of a portion of the combustion head of Figures 8 and 8a; Figure 11 is a schematic perspective view of a part of a burner, according to the present invention; Figure 12 is a cross-sectional side view of a portion of the discharge body of Figure 11; and Figures 13 and 13a are two graphs illustrating the temperature variation according to the distance from a furnace wall (distance is shown on the X-axis and temperature on the Y-axis). MA / 11 DETAILED DESCRIPTION OF THE INVENTION In Figure 1, the number (1) generally indicates a burner for baking ceramic articles T, according to a first aspect of the present invention. The burner (1) can preferably, but not necessarily, be installed in an industrial oven (2), in particular a tunnel oven, comprising a cooking chamber (3). In particular, as illustrated in Figures 1 and 2, the ceramic articles T are moved by means of a transport system (4), along a transport path P. More precisely, T ceramic items are any type of ceramic item that requires at least one firing in a kiln. In the non-limiting modality of Figures 1 and 2, the transport system (4) comprises a conveyor belt, on which the raw ceramic articles to be fired T are arranged, preferably in an orderly manner. According to some non-limiting, unillustrated modalities, the transport system (4) comprises a plurality of ceramic rollers (if necessary, also moved at different speeds to differentiate the firing of the articles). MA / 11 As illustrated in Figures 1 to 6a, the burner (1) comprises a mixing body (5), which in turn comprises a conduit (6) for supplying a fuel FL, preferably comprising a percentage of hydrogen, an oxidizer supply conduit (7), an activation device (8) for initiating combustion, and a flame detection device (9). The burner further comprises a combustion head (10). In other words, the mixing body (5) is the part of the burner necessary to generate the air and gas mixture that (after activation to produce a flame) will fire the ceramic articles T inside the kiln (2). In particular, the fuel introduced by means of the fuel supply conduit (6) is substantially methane gas, while the oxidizer introduced by means of the oxidizer supply conduit (7) is substantially ambient air (with approximately, for example, 21% oxygen). The burner (1) further comprises a tubular discharge element (11), which is adapted (configured to) allow the passage of a fluid F, which flows out of the mixing body (5) (formed from the fuel and oxidizer mixture and / or any combustion thereof), and is provided with an end (12) having an opening (13), within which at least a portion of the MA / 11 mixing body (5) (in particular of the combustion head (10)), is inserted, and an end (14) opposite the end (12) and having an opening (15). According to some non-limiting modalities, the mixing body (5) is coupled to the tubular discharge element (11) by means of fastening elements. Advantageously, but not necessarily, as in the modality illustrated in Figures 4, 4a and 5, 5a, the fastening elements are bolts (16). In the non-limiting embodiment illustrated in Figures 4, 4a and 5, 5a, the mixing body (5) is partially inserted within the discharge element (11) and partially disposed outside the furnace (2). In particular, in the embodiment of Figure 4, the discharge element (11) is inserted within a side wall (56) of the tunnel furnace (2). More precisely, the discharge element (11) extends completely within the side wall (56). In the non-limiting modality of Figures 5, 5a, on the one hand, the discharge element (11) extends through the length of the side wall (56), also partially entering the cooking chamber (3) of the oven (2). Advantageously, but not necessarily, the burner (1) comprises a tubular discharge element (18) (illustrated, for example, by a dotted line in the MA / 1 / ¿uzz / uauu ( Ί Figures 4a and 5a) extending from the end (14) of the element (11) in a direction opposite to the end (12), namely, towards (more precisely, into) the cooking chamber (3). In other words, the discharge element (18) is arranged on the opposite side of the discharge element (11), with respect to the mixing body (5). In some non-limiting cases, the burner (1) comprises a suction element (19), which is adapted (configured to) carry at least part of the gases G, G', present outside the burner (1), in particular outside the discharge element (11) and / or the discharge element (18) (more precisely inside the cooking chamber (3)), towards the tubular discharge element (18), and is provided with a plurality of openings (20), arranged between the element (11) and the tubular discharge element (18). Advantageously, but not necessarily, and as illustrated in the non-limiting modalities of Figures 4, 4a and 5, 5a, the tubular discharge element (14) is (completely) totally inside the cooking chamber (3) and, for example, is coaxial with the tubular discharge element (11). In other words, the longitudinal symmetry axis AA of the tubular discharge element (18) coincides with the longitudinal symmetry axis AA of the tubular discharge element (11). MA / 11 Advantageously, and in a manner completely different from the standards used in the ceramics market, the combustion head (10) is a multi-stage combustion head, namely, adapted (configured) to divide flame formation into different stages. In this way, it is possible to use air-stage technology to increase the flame speed to over 160 m / s, specifically to over 180 m / s, more precisely to approximately 200 m / s. In fact, the term "high speed," specifically with reference to burners, indicates a flame speed greater than or equal to 150 m / s. Advantageously, but not necessarily, the combustion head (10) is mounted at least partially inside the tubular discharge element (11), to be axial with it, along the longitudinal axis of symmetry AA of the burner (1). As illustrated in the non-limiting embodiments of Figures 4 to 10, advantageously, the multi-stage combustion head (10) comprises (at least) a combustion chamber (21), which is adapted (configured to) generate a first stage of flame combustion (in particular, to generate the so-called primeval flame), and (at least) a combustion chamber (22), which communicates with the combustion chamber (21) and is adapted (configured to) generate a second stage of flame combustion at the outlet of the combustion chamber (21). In particular, the combustion chambers (21) and (22) are configured to convey the flame at high speed within the tubular discharge element (11), towards the end (14), and in particular, through the suction element (19) towards the tubular discharge element (18). Advantageously, but not necessarily, and as illustrated in the non-limiting embodiments of Figures 4 to 8a, the FL fuel supply line (6) comprises a nozzle (17) for introducing the FL fuel into the combustion chamber (21). The nozzle (17) has an axial orifice (59) with a diameter smaller than 20 mm, in particular, smaller than 15 mm, and more specifically, smaller than or equal to 13.5 mm. This allows for an increase in the aforementioned hydrogen content of the FL fuel. Hydrogen, in particular, produces a much larger explosion than methane (or LPG), and it has been surprisingly observed that by increasing the FL fuel supply rate, the explosion can be appropriately counteracted, allowing for proper control and, at the same time, the injection of more fluid F into the combustion chamber (3). MA / 11 MA / 11 Advantageously, but not necessarily, the nozzle (7) for the introduction of FL fuel is obtained in one piece in a chamber (54) (in particular, made of aluminum) of the burner (1). In the non-limiting embodiment of Figure 8, in which a section of the multi-stage combustion head (10) is illustrated in detail, the combustion chamber (21) comprises at least one inlet opening (23) and one outlet opening (24) (more precisely, arranged on opposite sides of the combustion chamber (21)). In particular, the inlet opening (23) is adapted (configured to) communicate with the fuel supply conduit (6), and to receive a variable volumetric flow rate of the fuel. The outlet opening (24) is oriented towards the tubular discharge element (18) (or the cooking chamber (3)). In some non-limiting cases, such as in the one illustrated in Figure 8, the combustion chamber (21) and the combustion chamber (22) are coaxial with each other, and are arranged along the longitudinal axis AA of the burner (1). Advantageously, but not necessarily, the combustion chamber (21) also comprises a side wall (25), in particular cylindrical and / or frustoconical (or has MA / 11 (a complex form), provided with one or more oxidizer supply channels (26), configured to transport a portion OX' of the oxidizer OX to the combustion chamber, generating an oxidizer-fuel mixture M'. In particular, the oxidizer supply channels (26) are configured to transport (direct) the OX' portion of the oxidizer OX to the activation device (8) (and / or the flame detection device (9)). This facilitates ignition of the burner at high capacities. More precisely, the oxidizer supply channels (26) have different diameters. Advantageously, but not necessarily, the oxidizer supply channels (26) are configured to introduce the OX' portion of the oxidizer OX into the combustion chamber (21) at a velocity that has at least one component transverse to the symmetry axis AA of the burner (along which the fuel FL is injected). Advantageously, but not necessarily, a distribution element (60) is arranged along the supply conduit (7) of the oxidant OX to the combustion chamber (21) for distributing the oxidant OX. This element is provided with a plurality of through-openings (61) for dividing the oxidant OX flowing into the combustion chamber (21), particularly through the oxidant supply channels (26). More precisely, the openings (61) MA / 11 orifices have a width of less than 5 mm, particularly less than 4 mm, and preferably less than or equal to 3.5 mm. This allows for greater flame stability at minimum burner power levels, especially when the fuel FL has a particularly high hydrogen content. Specifically, it enables a more gradual and uniform distribution of the OX' portion of the OX oxidizer, thus minimizing the diversion of the FL fuel flow at minimum flow rates when larger orifices are present. In particular, the distribution element (60) comprises at least three, and in particular at least four, through-holes (61), which in particular are circular orifices. More specifically, the through-holes (61) are identical to each other and are distributed in the distribution element along at least one direction parallel to the longitudinal axis AA of the burner (1). In detail, without limitation, the through-holes (61) are arranged exclusively on the duct side (7). Advantageously, but not necessarily, the combustion chamber (22) comprises an inlet opening (27) and an outlet opening (28) opposite each other. The inlet opening (27) is configured to communicate with the outlet opening (24) and to receive the oxidizer-fuel mixture M'. The outlet opening (28) is oriented towards the tubular discharge element (18) (or the cooking chamber (3)). In some non-limiting cases, such as in the one illustrated in the modality of Figure 8, the combustion chamber (22) also comprises a side wall (29) having a substantially circular cross section; in particular, the cross section of the side wall (29) converges radially as it approaches the outlet opening (28). Advantageously, but not necessarily, the combustion chamber (22) is provided with one or more supply channels (30) for the oxidant OX, configured to transport a portion OX'' of the oxidant OX into the combustion chamber (22), generating together with the oxidant-fuel mixture M', an oxidant-fuel mixture M''. In particular, the supply channels (30) for the oxidizer OX are produced in such a way that the OX'' part of the oxidizer OX enters the interior of the combustion chamber (22) with a velocity that is at least partially transverse, with respect to a main direction of the oxidizer-fuel mixture M', which corresponds substantially to the longitudinal axis AA of the burner. According to the non-limiting modality of Figure 8, the side wall (29) of the combustion chamber (22), MA / 1 / ¿uzz / uauu ( Ί ma / t / zuzz / uauu / Ί has a substantially frustoconical shape, comprising a larger base (31) and a smaller base (32), wherein the larger base (31) is arranged in the inlet opening (27), while the smaller base (32) is arranged in the outlet opening (28). Advantageously, but not necessarily, the supply channels (30) for the oxidant OX are made to allow the OX'' part of the oxidant OX to enter the combustion chamber (22) at a speed that has a direction substantially parallel to the side wall (29) of the second combustion chamber. In the non-limiting embodiment of Figures 4 to 10, the burner (1), comprising a combustion chamber (33), is arranged downstream of the combustion chamber (22) and provided with an inlet opening (34) and an outlet opening (35), opposite each other. The inlet opening (34) is configured to communicate with the outlet opening (28) and to receive the oxidizer-fuel mixture M''. In particular, the outlet opening (35) is oriented towards the tubular discharge element (18) (or the cooking chamber (3)).More precisely, the combustion chamber (33) comprises a side wall (36) having a substantially circular cross-section, in particular cylindrical (or constantly parallel to the longitudinal axis AA of the burner (1)), and provided with one or more supply channels (37) for the oxidizer OX, configured to allow the entry of a portion OX'' ' ' of the oxidizer OX into the combustion chamber (33), generating, together with the oxidizer-fuel mixture M'', an oxidizer-fuel mixture M'' ' ' , which is generated within the combustion chamber (33), and which is transported to the tubular discharge element (18) (or to the cooking chamber (3)). Advantageously, but not necessarily, and as illustrated in the non-limiting modalities of Figures 1 to 5, the suction element (19) is adapted (configured to) be arranged, at least partially (in some cases, totally) within the cooking chamber (3). In the non-limiting embodiments of Figures 4, 5, 11, and 12, the tubular discharge element (11), the tubular discharge element (18), and the suction element (19) together form a combustion block (38), illustrated schematically in general in Figure 11. In particular, a lateral surface (39) of the combustion block (38) is (at least) partially unjointed. More specifically, the lateral surface (39) of the combustion block (38) is unjointed in the sections not interrupted by the openings (20). Advantageously, but not necessarily, the combustion block (38) is manufactured as a single piece, in MA / 11 particular made of silicon carbide. More precisely, the longitudinal axis of symmetry of the combustion block (38) is the longitudinal axis of symmetry AA of the burner (1), of the tubular discharge elements 11 and 18, and of the multi-stage combustion head (10). Advantageously, but not necessarily, the combustion block (38) is made by means of additive manufacturing, in particular, with 3D printing. According to some non-limiting, unillustrated modalities, the combustion block (38) is formed by welding the tubular discharge element (11) to the suction element (19), and the suction element (19) to the tubular discharge element (18). According to other non-limiting, unillustrated modalities, the combustion block (38) is formed by mechanical coupling, by means of fastening systems (for example, bolts, screws, rivets, etc.), of the tubular discharge element (11), with the suction element (19), and of the suction element (19) with the tubular discharge element (18). According to the additional non-limiting modalities, the combustion block (38) is formed by mold casting techniques. In the non-limiting modalities illustrated in the attached Figures, the combustion block (38) is hollow, and MA / 11 is adapted (configured to) allow the passage of a mixture (in particular, the M''' mixture) generated by the mixing body (5) (or by the combustion head (10)). In particular, the M', M'', M''' mixture, once combustion has been activated, becomes a flame. According to some non-limiting modalities, the suction element (19) comprises, in particular, a Venturi tube. In the non-limiting modality of Figures 11 and 12 (where Figure 12 illustrates a detail of the suction element (19) of the modality of Figure 11), the suction element (19) has a plug (40) disposed at the end (14). Furthermore, the suction element (19) has at least one section (41) that is frustoconical in shape, delimited by a larger base (42) and a smaller base (43). Finally, the tubular discharge element (18) has an open end (44) facing the suction element (19), and an open end (45) facing the center of the cooking chamber (3). Advantageously, but not necessarily, the openings (20) are elongated, or slotted, and pass transversely through the frustoconical section (41) of the suction element (19). In particular, the openings (20) are obtained MA / 11 longitudinally to the tubular discharge element (11), and to the tubular discharge element (18). More specifically, the smaller base (43) of the frustoconic section (41) coincides with the obturator (40), and the larger base (42) of the frustoconic section (41) coincides with the open end (44). Advantageously, but not necessarily, the openings (20) are provided in the frustoconical section (41) of the suction element (19). In particular, they pass through the frustoconical section (41) of the suction element (19) from side to side (transversely). Advantageously, but not necessarily, and as illustrated in Figures 3-5, 11, and 12, the suction element (19) comprises reinforcing ribs (46). Thanks to these ribs (46), it is possible to lengthen the discharge element (18) as desired without risking breakage of the combustion block (38) at the segment with the smallest cross-section, or at the suction element (19). Advantageously, but not necessarily, the discharge element (11) has a circular cross-section, in particular with a constant diameter. Advantageously, but not necessarily, the discharge element (18) has a circular cross-section, in particular with a constant diameter. Advantageously, but not necessarily, the MA / 11 suction element (19) has a circular cross-section. Advantageously, but not necessarily, the suction element (19) has a circular cross-section, with a substantially variable diameter. In particular, the cross-section TT (Figure 12) of the plug (40) has a diameter smaller than two-thirds of the diameter of the discharge element (18) and the diameter of the discharge element (11). More specifically, the cross-section TT (Figure 12) of the plug (40) has a diameter smaller than half the diameter of the discharge element (18) and the diameter of the discharge element (11). The more the diameter of the plug (40) is reduced relative to the diameter of the discharge element (11), the greater the increase in the variation of the mixture velocity M''', which, in use, circulates within the discharge element (11). Advantageously, but not necessarily, the cross-section TT (Figure 12) of the plug (40) has a diameter smaller than one-third of the diameter of the discharge element (18) and the diameter of the discharge element (11). In particular, the cross-section TT (Figure 12) of the plug (40) has a diameter larger than one-sixth of the diameter of the discharge element (18) and the diameter of the discharge element (11). MA / 11 MA / 11 Advantageously, but not necessarily, the diameter of the obturator (40) is smaller than 30 mm, specifically 25 mm or smaller. In detail, the diameter of the obturator (40) varies from 5 mm (specifically 10 mm; more specifically 20 mm) to 60 mm (specifically 40 mm; more specifically 30 mm). This feature also counteracts backfires and thus improves combustion management with hydrogen-rich FL fuel mixtures. Advantageously, but not necessarily, the diameter of the discharge element (11) and the diameter of the discharge element (18) varies from 20 mm (particularly 40 mm; more particularly 50 mm) to 200 mm (particularly 120 mm; more particularly 100 mm). In some non-limiting cases, the activation device (8) and / or the flame detection device (9) have an elongated shape and are inserted within the mixing body (5) along an electrode channel (47) and an electrode channel (48), arranged respectively along the axes AI and AR (illustrated in Figure 8), inclined at least partially (for example, by at least 500°) by an angle a and an angle β, respectively, with respect to the longitudinal axis AA of the burner (1). In some non-limiting cases, the angles a and β are substantially equal to each other. In other non-limiting cases, the angles a and β are different from each other. In particular, angles a and β are angles smaller than 45°. More specifically, angles a and β are angles smaller than 30°. More precisely, angles a and β are smaller than 20°. In detail, angles a and β are substantially equal to 15°. In the non-limiting embodiment of Figure 8, the activation device (8) comprises an activation electrode (49), and the flame detection device (9) comprises a detection electrode (50). In particular, the detection electrode (50) is longer (more precisely, twice as long) than the activation electrode (49). Advantageously, but not necessarily, the flame detection device (9) (more precisely, the detection electrode (50)) passes through at least the combustion chambers (21) and (22) and is configured to be at least partially tangent to the flame dart (or to the flame shape when operating at full capacity). In this way, it is possible to preserve the integrity of the flame detection electrode (50). Indeed, the fact that the detection electrode (50) remains tangent to the flame dart, without being immersed in it, limits wear on the electrode.In particular, as illustrated in the non-limiting modality of. MA / 11 MA / 11 Figure 8, the flame detection device (9) (more precisely the detection electrode (50)), also passes through the chamber (33) , and ends inside the tubular discharge element (11). In use, the detection electrode (50) provides data relating to the state of the flame generated by the burner, via which it is possible to adjust appropriately the flow rate of the fuel FL and / or the oxidant OX. According to a preferred, but not limiting, embodiment, as illustrated in Figures 4a, 5a, and 8a, the activation device (8) comprises an activation electrode (43), and the flame detection device (9) comprises a UV detection probe (50'). In particular, the UV probe (50') is disposed along the longitudinal axis AA of the burner, in a chamber (54), more precisely, but without limitation, above the mixing body (5). Advantageously, but not necessarily, the flame detection device (9) (more precisely, the UV detection probe (50')) is configured to receive a UV (ultraviolet radiation) beam from the flame, which passes through at least the combustion chambers (21) and (22). In operation, the UV detection probe (50') provides data regarding the state of the flame generated by the burner, allowing for appropriate adjustment of the fuel flow rate (FL) and / or the oxidizer (OX). Furthermore, in the case of flameless combustion at full operating capacity, the UV probe (50') is disabled because it is no longer possible to detect any flame, as the flame front dissipates within the oven's cooking chamber. In the non-limiting embodiments of Figures 9 and 10, two possible variations of the combustion head (10) are illustrated in the front section, in which the oxidant supply channels (30) have different inclinations relative to each other. Specifically, in Figure 9, one inclination axis ΆO of the channels (30) is inclined at an angle γ substantially equal to 30°, while in Figure 10, the inclination axis AO' of the channels (30) is inclined at an angle γ' substantially equal to 20°. In this case, the side wall (29) of the combustion chamber (22) and the oxidant supply channels (30) OX are substantially parallel. The above can obviously also be applied to the oxidant supply channels (37) OX. Advantageously, but not necessarily, the combustion chamber (33) comprises, in the side wall (36), a plurality of holes (51) arranged in one or more radial rows, preferably at equal distances. MA / 11 radial to one another. MA / 11 In the non-limiting embodiment of Figure 7, the combustion head (33) comprises a crown (52) configured to limit the entry of the oxidant OX into the tubular discharge element (11), which does not pass through the combustion chambers (21), (22), and (33). In particular, the crown (52) extends from the edge of the outlet opening (35) towards (a) the inner wall of the tubular discharge element (11). Advantageously, but not necessarily, and as illustrated in the non-limiting embodiment of Figure 7, the crown (52) comprises slots (53) (or any other type of opening), configured to carry a second portion OXIV of the oxidizer to the tubular discharge element (11), downstream of the combustion chambers (21), (22), and (33). In this way, together with the oxidizer-fuel mixture M''', the fluid F is generated flowing out of the tubular discharge element (11), through the suction element (19), into the tubular discharge (18). According to a second aspect of the present invention, an industrial apparatus for firing ceramic articles is provided. With particular reference to Figures 1 and 2, an industrial apparatus according to the present invention is generally indicated by the number (55). MA / 11 According to some non-limiting modalities, ceramic T articles, once fired, are tiles. In particular, ceramic articles T are raw at the entrance of the apparatus (55), and cooked at the exit. The industrial apparatus (55) comprises the oven (2) (described above), in particular a tunnel oven, provided with at least one side wall (56), which delimits the cooking chamber (3), and which has a surface (57) inside the cooking chamber (3) and a surface (58) outside the cooking chamber (3). The industrial apparatus (55) further comprises the transport system (4), in particular horizontal, which is configured to move the plurality of ceramic articles T, along the transport path P, within the cooking chamber (3) (from the entrance to the exit of the cooking chamber (3)). The transport system (4) can be any type of transport. For example, the transport system (4) comprises a conveyor belt (or a conveyor mesh), on which the raw ceramic articles T to be fired are arranged, preferably in an orderly manner. According to some non-limiting, unillustrated modalities, the transport system (4) comprises a plurality of ceramic rollers (if necessary, moved at different speeds to differentiate the firing of the articles). In particular, the tunnel kiln (2) has two opposing side walls (56), between which the ceramic T items move. According to some non-limiting, unillustrated modalities, ceramic articles are any type of ceramic articles that require at least one firing in the kiln. The apparatus (55) comprises a burner (1) which, in turn, comprises a tubular discharge element (11), and preferably, but not necessarily, a tubular discharge element (18), and a suction element (19) for gases G, G'. Advantageously, but not necessarily, the apparatus (30) comprises a burner (1) (hydrogen), as previously described. Advantageously, but not necessarily, the apparatus (55) comprises a hydrogen supply system, configured to inject hydrogen or a mixture comprising hydrogen, into the supply duct (6) for the EL fuel. Advantageously, but not necessarily, the suction element (19) is located between the element of MA / 11 MA / 11 discharge (11) and the discharge element (18), and is arranged at least partially (in some non-limiting cases also totally, as illustrated in Figure 5), inside the cooking chamber (3). Specifically, the suction element (19) is configured to carry at least some of the gases G, G' present within the cooking chamber (3) to the discharge element (18). This allows the residual oxygen within the cooking chamber (3) to be utilized, and the combustion of gases G, G' that were not completely burned during their initial passage through the burner (1) or through primary combustion can be completed. In addition, the gases G, G' (presumably also in view of the fact that they have a relatively high temperature) help to improve combustion efficiency. The term primary combustion indicates the combustion generated by the mixing body (5) (in particular, by the combustion head (10)), the flame of which passes through the discharge element (11). Advantageously, but not necessarily, and as illustrated in the non-limiting modality of Figure 4, the suction element (19) is arranged on the internal surface (57) of one of the side walls (56). In particular, the suction element (19) is configured to create a depression between the element of MA / 11 discharge (11) and the discharge element (18), to carry at least part of the gases G, G' present in the cooking chamber (3), towards the discharge element (18). In other words, in the non-limiting modes illustrated in the attached Figures, the depression is generated by the Venturi effect. The high speed of the flame generated by the multi-stage combustion head (10) has the surprisingly synergistic effect of increasing the suction capacity of the suction element (19). According to some non-limiting, unillustrated embodiments, the burner comprises several tubular discharge elements (18) within the cooking chamber (3), with several suction elements (19) positioned between them at intervals. According to the non-limiting embodiment of Figure 2, the apparatus (55) comprises a plurality of burners (1) arranged in series, along a direction DD parallel to the transport path P. In particular, the burners (1) are arranged at various levels within at least one of the walls (56) of the oven (2). In the non-limiting embodiments of Figures 1 to 5, the burner (1) is attached, by means of fastening elements, to the wall (56) of the oven (2). In particular, the discharge element (11) is inserted inside the wall (56). ma / t / zuzz / uauu / Ί In the non-limiting modality of Figure 1, the burners (1) are oriented in a transverse DP direction (in particular, perpendicular) to the DD direction (and, therefore, to the transport path P). Advantageously, but not necessarily, the tubular element (11) of the burner (1) is installed to pass through, at least partially (in particular, totally and transversely), one of the side walls (56) of the oven (2). In this way, the flame produced by the burner (1) will flow directly into the cooking chamber (3) of the oven (2). According to the non-limiting modalities illustrated in the attached Figures, the burner (1) has a longitudinal axis AA, which is transverse to the transport path P. In particular, the axis AA is perpendicular to the transport path P. More particularly, the axis AA is also perpendicular to the side wall (56) of the industrial tunnel furnace (2). Advantageously, but not necessarily, the tubular discharge element (18) of the burner (1) is coaxial with respect to the tubular discharge element (11), and is substantially fully disposed within the cooking chamber (3). According to some non-limiting, unillustrated modalities, the discharge element (11) of the burner (1) MA / 11 is installed to protrude partially into the cooking chamber (3). Advantageously, but not necessarily, the openings (20) are arranged at least partially (in particular, totally) within the cooking chamber (3). Advantageously, but not necessarily, the apparatus (55) (or each burner (1)) comprises at least one electronic control unit (62) configured to control the burner (1) to switch from a flame-cooking configuration to a flameless cooking configuration. In particular, the electronic control unit (62) is configured to extinguish the flame by reducing (preferably interrupting) the supply of fuel FL, and if necessary, oxidizer OX, selectively inhibit flame control (by means of the detection device (9)), and restore the supply of fuel FL and, if necessary, oxidizer OX, to allow the burner (1) to ignite in flameless mode.By using flameless combustion, or combustion that takes advantage of the fact that inside the furnace there is a higher temperature than the auto-ignition temperature of the fuel, it is possible to drastically reduce the NOx emissions normally generated in the combustion of hydrogen-rich mixtures (and in general, combustions with high flame peaks), thus allowing the use of an environmentally sustainable fuel with low emissions. Advantageously, but not necessarily, and as illustrated in the non-limiting embodiment of Figure 1, the apparatus comprises at least two temperature control devices (63), in particular, at least two double-filament thermocouples (64) arranged at at least two different significant points in the oven (2). These two points are such that they ensure that, at each point in the cooking chamber, the temperature is sufficiently higher than the auto-ignition temperature of the fuel mixture. Advantageously, but not necessarily, if the temperature detected by the two thermocouples (64) falls below the auto-ignition temperature, the flame is triggered and reignites, namely, the electronic control unit (62) immediately resets the burner (1) to flame operating mode. According to a further aspect of the present invention, a method is provided for firing ceramic articles transported within a tunnel kiln. The method comprises at least one step of supplying a burner as previously described, with a fuel comprising at least a percentage of MA / 11 MA / 11 hydrogen greater than 20%, in particular greater than 50%, and more specifically, greater than 70%. These fuel mixtures are made possible by the particular geometry of the burner described above, in particular, thanks to the multi-stage combustion head (10). Furthermore, the dimensions of the nozzle (17) (of the axial orifice (59)), the geometry of the distribution element, namely the size and number of through-holes (61), and the tubular discharge element (18) and the suction element (19), synergistically result in the important technical effect of reducing the environmental impact by allowing the use of a hydrogen-rich mixture as fuel and decreasing NOx. In some non-limiting cases, FL fuel comprises a hydrogen percentage greater than 90%. In particular, the fuel is 100% hydrogen. The method also comprises the step of simultaneously supplying the burner (1) with the oxidizer OX, and activating (igniting) the flame (by means of the activation device (8)), which extends at least partially into the burner and the cooking chamber (3) of the oven (2). Once the flame has been lit, the method involves controlling the flame with feedback, by means of the detection device (9). MA / 11 Advantageously, but not necessarily, the method comprises the additional steps, once the firing chamber (3) of the kiln (2) has reached a predefined temperature (in particular, higher than the auto-ignition temperature of the fuel FL), of extinguishing the flame by reducing (or interrupting) the supply of the fuel FL, and if necessary, the oxidizer OX; preferably, by disabling the aforementioned flame feedback control; and by re-establishing the supply of the fuel FL, in particular, also of the oxidizer, generating within the tunnel kiln (2), a flameless combustion that fires the ceramic articles T. In these non-limiting cases, this step represents the firing of the kiln (2) at full capacity.In this final step, in particular, the burner (1) is no longer mechanically ignited, and there is no longer a flame (or instead, a flame front) present and localized in the combustion head (10) and within the tubular discharge element (11), because it is diluted directly in the oven chamber with the combustion products already present in chamber (3), with a lower oxygen level than that of the combustion air. In other words, in this way, the oxidizer / fuel mixture flowing from the burner (1) into the cooking chamber (3) ignites within chamber (3). MA / 11 In this way, it is possible (as illustrated in the non-limiting configuration of Figure 13a, which shows the FB temperature profiles with the flame and FLB without the flame, as the distance from the side wall (56) of the furnace (2) increases) to avoid the presence of temperature peaks (which are one of the main causes of NOx production) compared to traditional flame-based solutions. Specifically, in Figure 13a, it can be observed from the FB profile that the temperatures obtained from flame combustion in the immediate vicinity of the discharge are extremely high (around 1,500°C near the discharge, and even 1,600°C–1,800°C inside the combustion block (38)). In contrast, in the flameless configuration, peak temperatures of approximately 1,250°C have been recorded inside the cooking chamber (3) of the furnace 4, while inside the burner (1), there are only a few hundred degrees, since no combustion is present.This, in turn, results in a lower thermal load on the burner components (1) (e.g., the combustion head (10), the mixing body (5), the combustion block (38), the oxidizer and fuel tubes, etc.). At the same time, a significant reduction in heat loss from the burner is achieved, thus improving the efficiency of the furnace (2). ML / 11 In the absence of a flame, the burner (1) will also be quieter, thus reducing the noise pollution produced by the latter. Furthermore, due to the lower compression within the combustion block (38), the power that can be supplied by a single burner is increased. Finally, the higher speed achieved to counteract the increased explosion caused by hydrogen allows greater penetration of the gases flowing out of the burner (1) into the cooking chamber (3), resulting in greater uniformity in the cooking of the T items. In use, the activation device (8) (in particular, the activation electrode) generates a spark which, together with the fuel FL flowing from conduit (6) and the oxidizer OX flowing from conduit (7), causes the flame to be generated. Specifically, the OX' portion of the oxidizer and the fuel FL generate the mixture M' within the combustion chamber (21), which defines a first flame stage, and continues to the combustion chamber (22), within which the mixture M' and the OX'' portion of the oxidizer combine to form the mixture M'', defining a second flame stage. The mixture M'', in the combustion, is transported to the combustion chamber (33), within which the mixture M'' and the OX'' portion of the oxidizer combine to form the mixture M'', which defines a second flame stage. MA / 11 oxidant combines (in particular, together with an additional portion of the oxidant flowing from the orifices (51)) to form the mixture M'', which in turn flows out of the combustion chamber (33) into the tubular discharge element (11), where, mixing with portion OXIV of the oxidant OX, it forms fluid F. The mixing body (5) thus generates a mixture that is at least partially burned, or a flame, fluids F from which are displaced through the discharge element (11), which introduces them into the suction element (19), which in turn transports them (along with the gases G, G' drawn from inside the cooking chamber (3)) to the discharge element (18). The latter introduces the flame into the combustion chamber. The combustion products emitted by the burner (1) are not completely burned during their first pass through the discharge element (11), but combustion is increased (terminated) due to the continuous recirculation of gases G, G' (present inside the cooking chamber (3)) through the suction element (19) to the discharge element (18). In other words, the burner (1) generates, via the activation device (8), primary combustion in the gases flowing from the ducts (6) and (7) (fuel and oxidizer), and secondary combustion of the same gases, utilizing the G, G' recirculated from inside the cooking chamber (3), which are not completely burned (and contain residual oxygen), and extracted by the suction element (19). Specifically, primary combustion takes place inside the discharge element (11), and secondary combustion takes place inside the discharge element (18). In particular, the combined action of the shutter (40) and the multi-stage combustion head (10) (which allows for a high combustion percentage to be achieved in less time due to premixing within the combustion chambers (21), (22), and (33)) results in an increase in the velocity of the fluid F emitted from the burner (1), which flows out of the discharge element (11). Subsequently, the gas velocity drops again due to the inclined, and specifically divergent, shape of the frustoconical section (41). Specifically, the use of a multi-stage combustion head (10) allows the shutter (40) to be further narrowed, creating an even greater depression. It has been hypothesized that the variation in the velocity of fluid F, which takes advantage of the Venturi effect, causes a depression in the openings (20). This depression, in turn, causes the suction of the gases G, G' present inside the chamber (3) and, therefore, allows a MA / 11 secondary combustion that takes advantage of the gases G, G' (in which a considerable percentage of oxygen is still present, approximately 10%). In the non-limiting configurations illustrated in the accompanying figures, the suction element (19) (due to the high fluid velocity F generated by the multi-stage combustion head (10)) causes an increase in turbulent flow within the firing chamber (3). Furthermore, the secondary combustion that takes place within the discharge element (18) generates an additional increase in heat exchange, particularly through radiation, due to the heating of the discharge element (18). This results in an increase in the overall heat exchange coefficient in the ceramic articles T, and greater temperature uniformity within the firing chamber (3). According to the advantageous non-limiting modality illustrated in Figures 3 and 4, the shutter (40) of the suction element (19) is positioned at the level of the inner surface (57) of the wall (56) of the furnace (2). This feature allows for the maximization of suction and recirculation of the gases G' present near the inner surface (57) of the wall (56) of the furnace (2), which are the gases with the lowest turbulence and, therefore, the lowest temperature. MA / 11 MA / 11 The graph in Figure 13 illustrates the temperature trend according to the distance from the wall (56) of the kiln (2); this graph was obtained experimentally. In particular, the Y-axis indicates the temperature of the ceramic articles T during firing, and the X-axis the distance from the wall (56). The temperature variation indicated by the dashed line SB refers to an apparatus with a standard burner, while the temperature variation indicated by the solid line IB refers to a non-limiting embodiment of the apparatus (55) according to the present invention. Therefore, it is evident that by using an apparatus (55) or a set of burners (1) according to the present invention, greater temperature uniformity is achieved across the width of the cooking chamber (3) of the oven (2). In particular, the temperature in the vicinity of the wall (56) is considerably increased due to the turbulence generated by the suction element (19) (thanks to the higher velocity permitted by the multi-stage combustion head (10)), and the contribution of the radiation provided by the discharge element (18) in the vicinity of the wall (56). Furthermore, the temperature in the center of the oven is increased compared to the traditional case, due to the use of the discharge element (18), which allows the combustion block (38) to reach greater depths within the oven (2). Therefore, the flame exiting the discharge element (14) is emitted to a greater depth than in traditional solutions. It is important to note that the temperature peak in the vicinity of the burner discharge (1) is also (at least partially) flattened. Although the invention described above refers in particular to a specific implementation example, it should not be considered limited to that implementation example, since all variations, modifications, or simplifications covered by the appended claims fall within its scope, such as, for example, a different geometry of the combustion head (10), the combustion block (38), and in particular, the suction element (19), a different method of suction of the gases G' in the vicinity of the internal surface (57) of the side wall (56), a different arrangement of the burners (1) within the apparatus (55) (in terms of both position and alignment), a different transport system (4), etc. The appliance and burner described above offer numerous advantages. First, the production and assembly of the burner (1) are simplified compared to the solutions of the technique MA / 11 is known, comprising several components. Furthermore, the burner (1), given its geometry and penetration into the cooking chamber (3), can be installed very simply to replace (as an improvement upon) a standard architecture. Furthermore, the presence of the discharge element (18) within the chamber (3) and the suction element (19) in the vicinity of the inner surface (57) of the wall (56), rather than within the wall (56), prevents problems related to overheating of the wall (56), which is usually made of brickwork. Overheating of the wall (56) could lead to ruptures of the combustion chamber (38) and / or overheating of the mixing body (5) (usually made of metal), which in turn would pose a risk of burns to operators and result in significant energy loss. Additionally, problems related to the formation of deposits and blockages caused by the condensation of recirculated gases within the brickwork of the side wall (31) are avoided. The additional advantages of the present invention are a reduction of dispersions, an increase in combustion (the recirculation obtained, at least 50% of the combustion products of the burner, allows the use of regulations with the reduction of the oxidant, taking advantage of the residual oxygen present in the recirculated gases G, G'), MA / 11 and uniformity of temperature within the cooking chamber (3), and these determine, in the part of the apparatus (55) and the burner (1) according to the present invention, the need for a smaller amount of gas (usually methane), to be introduced into the burner (1) to maintain a given temperature, with respect to solutions of the known art. Furthermore, the use of a multi-stage combustion head (10) allows for the reduction of flame temperature peaks, which are the primary cause of nitrogen oxide formation. Therefore, the present invention achieves a reduction in nitrogen oxides (NOx), specifically to below 50 ppm. Furthermore, the synergistic effect between the multi-stage combustion head (10) and the combustion block (38) allows for the use of very small discharges. In particular, in some non-limiting cases, the shutter diameter is 25 mm. This is due to the high velocity achievable through the air-stage technique, which allows for a flame speed of approximately 200 m / s. The present invention is configured to be supplied with different types of gas (e.g., methane or LPG), and is designed to operate with environmentally sustainable fuels, such as, for example MA / 11 example, hydrogen-enriched methane, pure hydrogen, etc. In particular, the shape of the oxidant supply channels varies depending on the fuel used. In comparison with a traditional burner, the flame of the burner according to the present invention is more uniform and less swirling. This characteristic allows the flame to remain defined and spread further without opening up too much into the surrounding environment (or the firing chamber (3)). This means that ceramic items in transit during firing are minimally affected by direct flame contact, thus preventing potential technological defects (color shading, size variations, etc.) caused by frequent temperature spikes resulting from direct flame exposure. Furthermore, the high recirculation created by the very high flame speed of the burner (1), which comprises a combustion block as described above, dilutes the flame temperatures (or reduces the peaks, increasing the average), and increases the convective heat exchange coefficient with the ceramic articles T. For this reason, compared to a traditional design and with the same power output, the present invention allows for greater heating of the material without attacking it with the MA / 11 flame temperature peaks, oxidizing the organic substances contained in the ceramic T articles in a more uniform manner, and therefore preventing the appearance of a dark coloration in the internal portion of an article when viewed in section. In this way, the risk of explosion of ceramic articles T in a preheating area of ​​the oven (2), for example, when articles with excessive moisture content are placed in the oven, is also partially inhibited. Furthermore, due to the high recirculation of the generated gas, the combustion products tend to stratify horizontally, without creating vertical movement from a lower chamber of the furnace to an upper chamber in the vicinity of the walls. For this reason, the appearance of imperfections (small cracks) on the lateral edges of the articles adjacent to the side walls (56) of the furnace (2), especially in the preheating areas, is at least partially inhibited. Since the burner (1) maintains a high flame speed even at low work capacity (e.g., during production gaps), the furnace crown (2) is not (substantially) thermally stressed by direct flame interaction. Consequently, the apparatus (55) of MA / 11 MA / 11, in accordance with the present invention, also allows for greater uniformity in the firing of ceramic articles, especially in wide-mouth kilns. This feature provides the additional advantage of being able to reduce the height of the kiln chamber (3) (2), further increasing the exchange between the gases G and the ceramic articles T during firing without risking damage to the kiln crown or the articles themselves due to unwanted flame plumes. Finally, the reduction of the oven chamber results in the following advantages: reduction of the volumes within the chamber, therefore, improved convective heat exchange with the material, and the consequent reduction of specific consumption.

Claims

1. A burner (1) for firing ceramic articles (T), which can be installed in an industrial kiln (2), comprising a firing chamber (3); the burner (1) comprises: a mixing body (5); which in turn comprises at least one conduit (6) for supplying a fuel (FL); at least one conduit (7) for supplying an oxidizer (OX); an activation device (8) for starting combustion; a flame detection device (9); a first tubular discharge element (11), which is configured to allow the passage of a fluid (F) flowing from the mixing body (5), and which is provided with a first end (12), into which at least part of the mixing body (5) is inserted, and a second end (14) opposite the first end (12); the burner (1) also comprises at least a second tubular discharge element (18), which extends from the second end (14) on the opposite side with respect to the first end (12);and a suction element (19), which is configured to carry at least part of the gases (G, G') present outside the burner (1), towards the second tubular discharge element (18), and is provided with one or more openings (20) arranged between the first (11) and second (18) tubular discharge elements; the mixing body (5) comprises a multi-stage combustion head (10) arranged at least partially within the first tubular discharge element (11).

2. The burner (1) according to claim 1, wherein the multi-stage combustion head (10) comprises at least a first combustion chamber (21), configured to generate a first combustion phase of a flame, and at least a second combustion chamber (22), which communicates with the first combustion chamber (21), and configured to generate a second combustion phase of the flame exiting the first combustion chamber (21); the first and second combustion chambers (21, 22) are configured to transport the flame at high speed within the first tubular discharge element (11) and, passing through the suction element (19), towards the second tubular discharge element (18).

3. The burner (1) according to claim 1 or 2, wherein the first combustion chamber (21) comprises a first inlet opening (23) and a first outlet opening (24); the first inlet opening (23) is configured to communicate with the conduit (6) for supplying fuel and for receiving a volumetric flow rate, in particular variable, of the fuel (FL); the first outlet opening (24) is oriented towards the second tubular discharge element (18); the first combustion chamber (21) also comprises a first side wall (25), in particular cylindrical, provided with one or more first oxidizer (OX) supply channels (26), which are configured to carry a first portion (OX') of the oxidizer (OX) into the first combustion chamber (21), generating a first fuel-oxidizer mixture (OX) (M');In particular, the first combustion chamber (21) and the second combustion chamber (22) are coaxial with each other, and are arranged along a longitudinal axis (AA) of the burner (1); in particular, the first oxidant (OX) supply channels (26) are configured to transport the first part (OX') of the oxidant (OX) in correspondence to the activation device (8).

4. The burner (1) according to claim 2 or 3, wherein the second combustion chamber (22) comprises a second inlet opening (27) and a second outlet opening (28); the second inlet opening (27) is configured to communicate with the first outlet opening (24) and to receive the first fuel-oxidizer mixture (M'); the second outlet opening (28) is oriented towards the second tubular discharge element (18); the second combustion chamber (22) also comprises a second side wall (29) having a substantially circular cross-section, in particular MA / 11 converging radially towards the second outlet opening (28);The second combustion chamber (22) is provided with one or more second oxidant (OX) supply channels (30), which are configured to carry a second part (OX'') of the oxidant (OX) into the second combustion chamber (22), generating, together with the first oxidant-fuel mixture (M'), a second oxidant-fuel mixture (M''); in particular, the second oxidant (OX) supply channels (30) are made in such a way that they allow the second part (OX'') of the oxidant (OX) to enter the second combustion chamber (22) at a speed that has at least one tangential component with respect to a principal direction of the first oxidant-fuel mixture (M'), or with respect to a longitudinal axis (AA) of the burner (1).

5. The burner (1) according to claim 4, wherein the second side wall (29) of the second combustion chamber (22) has a frustoconical shape comprising a larger base (31) and a smaller base (32); wherein the larger base (31) is in the second inlet opening (27), while the smaller base (32) is disposed in the second outlet opening (28); in particular, the second oxidant (OX) supply channels (30) are made in such a way as to allow the second part (OX'') of the oxidant (OX) to enter the second combustion chamber (22) at a velocity substantially parallel to the second side wall (29) of the second combustion chamber (22).

6. The burner (1) according to any of claims 2 to 5, comprising a third combustion chamber (33) located downstream of the second combustion chamber (22), and provided with a third inlet opening (34) and a third outlet opening (35); the third inlet opening (34) is configured to communicate with the second outlet opening (28), and to receive the second oxidizer-fuel mixture (M''); the third outlet opening (35) is oriented towards the second tubular discharge element (18);The third combustion chamber (33) comprises a third side wall (36) having a substantially circular, in particular cylindrical, cross-section and provided with one or more third oxidant (OX) supply channels (37), which are configured to allow a third part (OX''') of the oxidant (OX) to enter the third combustion chamber (33), generating together with the second oxidant-fuel mixture (M''), a third oxidant-fuel mixture (M'''), which is transported to the second tubular discharge element (18).

7. The burner (1) according to any of the preceding claims, wherein the MA / 11 suction element (19) is configured to be arranged, at least partially, within the cooking chamber (3).

8. The burner (1) according to any of the preceding claims, wherein the first tubular discharge element (11) is coaxial with the second tubular discharge element (18) and with the multi-stage combustion head (10); in particular, the first tubular discharge element (11), the second tubular discharge element (18), and the suction element (19) form a combustion block (38) having a lateral surface (39) that is at least partially seamless.

9. The burner (1) according to any of the preceding claims, wherein the first tubular discharge element (11), the second tubular discharge element (18) and the suction element (19) form a combustion block (38) manufactured as a single piece, in particular made of silicon carbide; the combustion block (38) is coupled to the mixing body (5).

10. The burner (1) according to any of the preceding claims, wherein the suction element (19) has a shutter (40) disposed at the second end (14); the suction element (19) has at least one frustoconical section (41), which is delimited by a larger base (42) and a smaller base (43); MA / 11 the second tubular discharge element (18) has a first open end (44), oriented towards the suction element (19), and a second open end (44) oriented towards the interior of the cooking chamber (3).

11. The burner (1) according to claim 10, wherein the openings (20) extend through the suction element (19) (e.g., they are elongated and arranged longitudinally to the first tubular discharge element (11) and the second tubular discharge element (18); the smaller base (43) of the frustoconical section (41) coincides with the obturator (40); the larger base (42) of the frustoconical section (41) coincides with the first open end (44); in particular, the openings (20) are arranged in the frustoconical section (41).

12. The burner (1) according to any of the preceding claims, wherein the activation device (8) and / or the flame detection device (9) have an elongated shape and are inserted within the mixing body (5), respectively along a first channel (47) and a second channel (48), arranged along the axes (AI, AR), at least partially inclined with respect to a longitudinal axis (AA) of the burner (1); in particular the flame detection device (9) passes through at least a first combustion chamber (21) and a second combustion chamber (22), and is configured to be at least partially tangent to a flame dart.

13. An industrial apparatus (55) for firing ceramic articles (T), comprising: a tunnel kiln (2) provided with at least one side wall (56), which at least partially delimits a firing chamber (3), and which has an inner surface (57) inside the firing chamber (3) and an outer surface (58) outside the firing chamber (3); a conveying system (4), which is configured to move a plurality of ceramic articles (T) along a conveying path (P) within the firing chamber (3); the kiln (2) comprises at least one burner (1), according to any one of claims 1 to 12; the suction element (19) is disposed between the first tubular discharge element (11) and the second tubular discharge element (18) and is disposed, at least partially, within the firing chamber (3);The suction element (19) is configured to carry at least part of the gases (G, G') present in the cooking chamber (3) towards the second tubular discharge element (18).

14. The apparatus (55) according to claim 13, wherein the suction element (19) is disposed on the MA / 11 inner surface (57) of the side wall (56); the suction element (19) is configured to create a depression between the first discharge element (11) and the second discharge element (18), to carry at least part of the gases (G, G') present in the cooking chamber (3) towards the second discharge element (18); in particular, the apparatus (55) comprises a plurality of burners (1) arranged in series along a direction (DD) that is parallel to the transport path (P); in particular, the burner (1) has a longitudinal axis (AA) that is transverse (in particular, perpendicular) to the transport path (P), for example, perpendicular to the wall (56) of the industrial oven (2).

15. The apparatus (55) according to claim 13 or 14, wherein the first tubular discharge element (11) of the at least one burner (1) extends at least partially (in particular, totally) through (in particular, transversely to) the side wall (56) of the oven (2); the second tubular discharge element (18) of the burner (1) is substantially coaxial with respect to the first tubular discharge element (11), and is substantially disposed within the cooking chamber (3).

16. The apparatus (55) according to any of claims 13 to 15, wherein the first tubular discharge element (11) of the at least one burner (1) is installed to protrude partially into the cooking chamber (3).

17. The burner (1) for firing ceramic articles (T), which can be installed in an industrial kiln (2), comprising a firing chamber (3); the burner (1) comprises: a mixing body (5); which in turn comprises at least one conduit (6) for supplying a fuel (FL) comprising a percentage of hydrogen; at least one conduit (7) for supplying an oxidizer (OX); an activation device (8) for starting combustion; a flame detection device (9); a first tubular discharge element (11), which is configured so that a fluid (F) flowing from the mixing body (5) passes through it, and which is provided with a first end (12), into which at least part of the mixing body (5) is inserted, and a second end (14), which is opposite the first end (12);The burner (1) has a mixing body (5) comprising a multi-stage combustion head (10), which is disposed at least partially within the first tubular discharge element (11); wherein the multi-stage combustion head (10) comprises the MA / 11 less a first combustion chamber (21), which is configured to generate a first combustion stage of a flame, and at least a second combustion chamber (22), which communicates with the first combustion chamber (21), and is configured to generate a second combustion stage of the flame, which exits the first combustion chamber (21); the first and second combustion chambers (21, 22) are configured to transport the flame within the first tubular discharge element (11) towards the second end (14).

18. The burner (1) according to claim 17, wherein the fuel supply conduit (6) comprises a nozzle for introducing fuel into the first combustion chamber (21), the nozzle having an axial orifice with a diameter smaller than 20 mm, in particular smaller than 15 mm, more particularly smaller than or equal to 13.5 mm.

19. The burner (1) according to claim 18, wherein the fuel inlet nozzle is obtained in a burner chamber, as a single piece together with the latter.

20. The burner (1) according to any of claims 17-19, wherein an oxidizer distribution element is disposed along the oxidizer supply conduit to the first combustion chamber, the element being provided with a plurality of through-holes for dividing the oxidizer flowing into the first combustion chamber; wherein the hole width is less than 5 mm, in particular less than 4 mm, preferably less than or equal to 3.5 mm.

21. The burner according to claim 20, wherein the distribution element comprises at least three, in particular, at least four through openings; in particular, the openings are circular holes.

22. The burner according to any of claims 17-21, wherein the flame detection device comprises a UV probe, in particular arranged along a longitudinal axis of the burner, above a mixing body chamber.

23. The burner according to any of claims 17-22, wherein the first tubular discharge element has a plug disposed at the second end; the plug permits the second end to have a diameter that is smaller than 30 mm, in particular equal to or smaller than 25 mm.

24. The burner according to any of claims 17-23, further comprising at least a second tubular discharge element (18) extending from the second end (14) on the opposite side with respect to the first end (12); and a suction element (19) configured to carry at least some of the gases (G, G') present outside the burner (1) to the second tubular discharge element (18), and provided with one or more openings (20) arranged between the first (11) and second (18) tubular discharge elements.

25. The burner (1) according to any of claims 17-24, comprising a third combustion chamber (33), which is disposed downstream of the second combustion chamber (22), and is provided with a third inlet opening (34) and a third outlet opening (35); the third inlet opening (34) is configured to communicate with the second outlet opening (28), and to receive the second fuel-oxidizer mixture (M''); the third outlet opening (35) is oriented towards the second tubular discharge element (18).

26. An industrial apparatus (55) for firing ceramic articles (T), comprising: a tunnel kiln (2) provided with at least one side wall (56), which at least partially delimits a firing chamber (3), and which has an inner surface (57) inside the firing chamber (3), and an outer surface (58) outside the firing chamber (3); a transport system (4), which is configured to move a plurality of ceramic articles (T) along a transport path (P) within the firing chamber (3); the apparatus (55) comprises at least one burner (1), according to any one of claims 17 to 25; the industrial apparatus (55) comprises at least one hydrogen supply system, which is configured to inject hydrogen or a mixture comprising hydrogen into the fuel supply conduit.

27. The apparatus (55) according to claim (26), wherein a suction element is disposed between the first tubular discharge element (11) and a second tubular discharge element (18) and at least partially within the cooking chamber (3); the suction element (19) is configured to carry at least part of the gases (G, G') present in the cooking chamber (3) towards the second discharge element (18); in particular, the suction element (19) is disposed on the inner surface (57) of the side wall (56); the suction element (19) is configured to create a depression between the first discharge element (11) and the second discharge element (18) to carry at least part of the gases (G, G') present in the cooking chamber (3) towards the second discharge element (18);In particular, the apparatus (55) comprises a plurality of burners (1) arranged in series along MA / 11 in a direction (DD), which is parallel to the transport path (P); in particular, the burner (1) has a longitudinal axis (AA) transverse (in particular, perpendicular) to the transport path (P), for example, perpendicular to the wall (56) of the industrial furnace (2).

28. The apparatus (55) according to claim 26 or 27, comprising at least one electronic control unit, configured to control the burner (1) to switch from a flame cooking configuration to a flameless cooking configuration; in particular, the electronic control unit is configured to extinguish the flame by reducing the fuel supply and, if necessary, the oxidizer supply, and to restore the fuel supply and, if necessary, the oxidizer supply, allowing the burner to ignite in flameless mode.

29. The apparatus according to claim 28, comprising at least two temperature control devices, in particular double-filament thermocouples, arranged at at least two different points in the tunnel furnace.

30. A method for firing conveyor ceramic articles (T) within a tunnel kiln, comprising the steps of: supplying a burner, in particular according to any 6 4 of claims 17 to 25, with a fuel comprising at least a hydrogen percentage greater than 20%, in particular, greater than 50%, more particularly, greater than 70%; simultaneously supplying the burner with an oxidizer and igniting a flame at least partially within the burner and a firing chamber of the tunnel kiln; controlling the flame with feedback.

31. The method according to claim 30, comprising, once the firing chamber of the kiln has reached a certain temperature, the further steps of: extinguishing the flame by reducing the supply of fuel and, in particular, of the oxidizer; and restoring the supply of fuel and, in particular, of the oxidizer, generating within the tunnel kiln, a flameless combustion that fires the MA / 11 ceramic articles.

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