Technical Field

The present invention relates to a burner for industrial kilns, dryers and the like. Background Art

In the sector of the realization of systems and devices such as industrial kilns, dryers, and the like, with particular but not exclusive reference to the production of articles such as ceramic tiles, sanitary ware, and others, burners are used which, using a gaseous fuel such as e.g. natural gas, generate thermal energy and deliver it inside a portion of the system or device (known as firing chamber, or drying chamber, etc.), in which the products being processed are located or through which they transit.

The aforementioned burners are installed, in a suitable number, inside the system or device according to the most suitable configuration in relation to the type of product treated, and in relation to the treatment methods of the same; in the most typical applications, the burners are housed inside respective through openings formed in the side walls of the system or device, with the respective nozzles, if any, relating to the inner chamber.

Each burner usually comprises a main body, for example a tubular or substantially tubular body, provided with a first fuel inlet port, and with a second port for the entry of the oxidizing element, i.e. normally air (if necessary preheated to a certain temperature).

The aforementioned first port communicates with a fuel supply manifold, typically coaxial to the main body; such manifold flows into a final supply element, provided with holes.

In the proximity of the fuel supply end element, a diffuser can be installed along the air outlet adapted to generate a turbine, so as to facilitate the mixing of the air with the fuel.

More in detail, the diffuser is sized and mounted in such a way as to circumscribe the fuel supply end element, so as to keep the air and fuel outlets very close to each other.

Moreover, in the proximity of the dispensing element, ignition means are provided, which determine the ignition of a spark that ignites the mixture. The burner can also comprise a nozzle, connected coaxial to the main body, and provided with an outlet; by suitably sizing the nozzle, by means of such outlet, it is possible to reach the desired position inside the chamber of the system or device.

The burners of the type described above have some drawbacks, mainly related to the limited power range within which they have an optimal and regular, or in any case satisfactory behavior, free of malfunctions in relation to the specific application.

More in detail, in situations wherein the need exists to operate at high power, it is necessary to increase the flow of combustible gas which reaches the burner; consequently, for obvious reasons related to the stoichiometry of the reaction, it is also necessary to increase the flow rate of incoming air.

Since, as mentioned, the air enters the burner through the diffuser which surrounds the gas supply end element, the increase in its flow rate, beyond a certain limit, causes phenomena of accentuated turbulence mainly in the area of flame generation.

These phenomena of turbulence are decidedly troublesome, since they negatively affect the burner’s performance and compromise its operating stability.

In the opposite situation, i.e. that of low power operation, a small flow rate of gas is introduced into the burner: in this condition, the speed of the air introduced through the same diffuser can sometimes cause the accidental extinguishing of the burner flame, with consequent considerable inconvenience for production, or malfunctions of the system or device.

Description of the Invention

The technical aim of the present invention is to improve the state of the art in the field of burners for industrial kilns, dryers and the like.

Within the scope of this technical aim, it is one object of the present invention to provide a burner for industrial kilns, dryers and the like that are more versatile than the burners currently used.

Another object of the present invention is to provide a burner for industrial kilns, dryers and the like that can operate optimally in a wider power range than burners currently used.

Another object of the present invention is to provide a burner for industrial kilns, dryers and the like which allows reducing or eliminating the harmful phenomena of turbulence due to the speed of the combustion air introduced through the diffuser.

A further object of the present invention is to provide a burner for industrial kilns, dryers and the like which allows reducing or eliminating the harmful phenomena of accidental extinction of the flame under low-power operating conditions.

This aim and such objects are all achieved by a burner for industrial kilns according to the attached claim 1.

The burner comprises a body, provided with a first passageway for the supply of primary combustion air, ending in a first outlet section.

Furthermore, the burner comprises a manifold for the supply of the fuel, provided with a gas supply end element, surrounded by the aforementioned first outlet section.

The burner also comprises triggering means for triggering the combustion of the fuel- oxidizing element mixture, and a nozzle, connected to the above body, provided with an outflow port adapted for the combustion products generated inside the burner to come out.

According to one aspect of the invention, the burner body comprises a second passageway for the supply of secondary combustion air, ending in a second outlet section arranged at the periphery of the first outlet section; the first outlet section and the second outlet section are adapted to diffuse the primary air and the secondary air respectively inside the nozzle.

According to another aspect of the invention, the burner comprises a first duct for the supply of primary air, and a second duct for the supply of secondary air; the first duct comprises a first device for regulating the primary air flow rate, while the second duct comprises a second device for regulating the secondary air flow rate.

The first regulation device comprises a first butterfly valve, while the second regulation device comprises a second butterfly valve. The regulation of the primary air flow rate and of the secondary air flow rate, independently of each other, permits reducing or eliminating all the drawbacks affecting the burners of known type currently used.

More in particular, and as better explained below, it is possible to make a precise balance between the two flow rates so that the secondary air, which is introduced into the nozzle through a peripheral outlet section with respect to that of the primary air, compensates for the lack of combustion air resulting from the regulation of the primary air flow rate; the latter is instead limited according to two typical situations so as not to generate turbulence in the center of the nozzle in case of high power demand, or not to cause the accidental extinguishment of the flame, in case of low power demand.

The dependent claims relate to preferred and advantageous embodiments of the invention.

Brief Description of the Drawings

Further characteristics and advantages of the present invention will become more clear from the detailed description of some preferred but not exclusive embodiments of a burner for industrial kilns, dryers and the like, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a diameter section of the burner;

Figure 2 is a detail of Figure 1 ;

Figure 3 is an axonometric view of the burner, with the nozzle removed for greater clarity;

Figure 4 is an axonometric view of another embodiment of the burner according to the invention, with the nozzle removed for greater clarity.

Embodiments of the Invention

With reference to the attached figures, reference numeral 1 globally indicates a burner for industrial kilns, dryers and the like according to the present invention.

The burner 1 according to the present invention is suitable, however in a non exclusive way, to be used in firing kilns of industrial products.

For example, the burner 1 of particularly effective and advantageous use in the context of firing kilns for ceramic products such as ceramic tiles, sanitary ware, and the like.

The burner 1 can be used effectively, for example, in radiant tube dryers for ceramic products or the like.

Further uses in different sectors cannot however be ruled out, wherein the burner 1 according to the invention is equally effective.

The burner 1 comprises a body 2.

The body 2 is, e.g., of cylindrical or substantially cylindrical tubular shape.

In some embodiments of the invention, the body 2 could however have a different shape or geometry than the cylindrical tubular one, in relation to specific application requirements.

For ease of reference and for better understanding, the cylindrical symmetry axis of the body 2 is called the longitudinal axis A of the burner 1.

Conventionally, in the remainder of the present description, the adjective “distal” relates to the parts of the burner 1 facing the firing chamber, and therefore towards the inside of the kiln (not shown in the illustrations), while the adjective“proximal” relates to the parts of the burner facing the outside of the kiln.

The body 2 comprises a proximal portion 3; at the proximal portion 3 are provided the fluid inlet sections, i.e. the fuel and the oxidizing element.

Moreover, the body 2 comprises a distal portion 4, opposite the proximal portion 3.

The burner 1 comprises at least one first port 5, for the entry of the primary combustion air.

The burner further comprises a second port 6, for the entry of the secondary combustion air.

The burner comprises, in addition, a third port 7, for the entry of the fuel.

According to one aspect of the invention, the burner 1 comprises a nozzle 8.

The nozzle 8 is connected to the body 2, at the distal portion 4 of the latter.

The nozzle 8 can be connected to the body 2 in a removable manner, e.g. with a connection of the flanged type.

The size and shape of the nozzle 8 can be modified to reach different areas inside the firing kiln, or to modify/optimize the behavior of the combustion products coming out of the burner 1.

The first port 5 and the second port 6 are provided in the body 2.

More particularly, the first port 5 and the second port 6 are provided along the lateral surface of the body 2.

The body 2 comprises, at its proximal portion 3, a first end 9.

Moreover, the body 2 comprises, at its distal portion 4, a second end 10; more specifically, at least the second end 10 is flanged, and permits obtaining the connection with the nozzle 8.

A closure element 11 is connected to the first end 9 which can also be shaped as a flange.

The closure element 11 comprises the third port 7 for the fuel inlet.

According to an aspect of the invention, the body 2 of the burner 1 comprises a first passageway 12 for the primary air.

The first passageway 12 places the first port 5 in fluidic communication with a first outlet section 13 of the primary air.

Moreover, the body 2 of the burner 1 comprises a second passageway 14 for the secondary air.

The second passageway 14 places the second port 6 in fluidic communication with a second outlet section 15 of the secondary air.

The burner 1 further comprises a fuel manifold 16.

The fuel can be for example natural gas, or even another fluid fuel suitable for the specific application of use of the burner 1.

The manifold 16 communicates with the third port 7; moreover, the manifold 16 comprises an end element 17, adapted to dispense the fuel gas.

The manifold 16 is arranged coaxial with the longitudinal axis A of the burner

1.

The end element 17 can comprise, for example, a number of holes 18 for the supply of combustible gas; such holes 18 can be arranged in different positions, e.g., parallel to the longitudinal axis A, or perpendicular to the latter, or yet in other positions.

The conformation of the end element 17 can however be any, in relation to specific functional requirements; also the conformation of the manifold 16 can be any.

The burner 1 comprises ignition means 19 for the combustion of the fuel- oxidizing element mixture.

The ignition means 19 are housed inside the body 2 of the burner 1; the ignition means 19 comprise a first connecting element 20, passing through a corresponding opening provided for in the closure element 11.

The ignition means 19 are adapted to determine the ignition of a spark which ignites the mixture.

The burner 1 also comprises flame detection means 21.

The flame detection means 21 are also housed inside the body 2 of the burner 1; the flame detection means 21 comprise a second connecting element 22, passing through a second respective opening provided in the closure element 11.

The ignition means 19 and the detection means 21 can both be operatively connected, respectively through the first connecting element 20 and the second connecting element 22, to a control and management unit for the operation of the kiln, or other firing device, inside which the burner 1 operates (not shown in the figures).

According to one aspect of the invention, the first passageway 12 and the second passageway 14 are separated from each other inside the body 2 by means of a partition 23.

The partition 23 has a tubular or substantially tubular conformation; more in detail, the partition 23 comprises - or consists of - a cylindrical or substantially cylindrical wall.

The partition 23 has a surface cross-section smaller than that of the body 2; more particularly, the partition 23 is housed inside the body 2, preferably, the partition 23 is coaxial with the body 2.

Consequently, a gap 24 is defined between the body 2 and the partition 23; the gap 24 therefore has a circular crown-shaped section.

Therefore, the first passageway 12 is defined internally to the partition 23, while the second passageway 14 is defined externally to the partition 23, that is along the gap 24.

In other words, assuming we observe the burner 1 in section, the first outlet section 13 - where the first passageway 12 ends - surrounds the end element 17 of the manifold 16; the second outlet section 15, where the second passageway 14 ends, is in turn located at the periphery of the first outlet section 13.

The burner 1 comprises a cage element 25, to which the partition 23 is connected, with its innermost or proximal end.

The cage element 25 is adapted to place the first port 5, provided in the lateral surface of the body 2, in communication with the inner volume of the partition 23, so as to create the first passageway 12.

The cage element 25 has an essentially cylindrical conformation; the cage element 25 comprises a plurality of lateral openings 26, which allow the primary air, coming from the first port 5, penetrating inside it.

The cage element 25 is fixed, with a base thereof, to the proximal portion 3 of the body 2, or to the rear closure element 11.

Moreover, at the other opposite base, the cage element 25 comprises a disc shaped portion 27, having a larger diameter than that of its central part, which abuts at a respective shoulder 28 provided in the inner surface of the body 2.

The burner 1 comprises means for generating a turbine within the flow of the fuel- oxidizing element mixture, adapted to facilitate the process of mixing of the two gases.

The turbine generating means comprise, more in detail, a first diffuser 29.

The first diffuser 29 is associated with the distal end of the partition 23 in use.

As can be seen in Figure 2, the first diffuser 29 is substantially disc-shaped, and comprises, along its outer lateral surface, a plurality of first peripheral slits 30. The first slits 30 define respective channels inclined with respect to the longitudinal axis A of the burner 1; a certain tangential component is then imparted to the air which passes through said first slits 30 with a certain speed, and this determines the formation of a turbine.

The first diffuser 29 also comprises a plurality of further holes 31.

The holes 31 are distributed in the central area of the first diffuser 29.

Furthermore, the first diffuser 29 comprises a central opening, which allows the end element 17 of the manifold 16 to come out.

As better described below, the partition 23 has a length such as to protrude, for a certain distance, from the body 2 of the burner 1, and to penetrate inside the nozzle 8.

The turbine generating means also comprise a second diffuser 32.

The second diffuser 32 is associated with the distal opening, in use, of the body

2.

The second diffuser 32 is substantially circular crown-shaped, and therefore defines a central opening; at the inner edge of this central opening, the second diffuser 32 comprises a plurality of second slits 33.

The second slits 33 also define respective channels inclined with respect to the longitudinal axis A of the burner 1, so as to impart a certain tangential component to the air which passes through them.

The second diffuser 32 is positioned so that the tubular partition 23 passes through its central opening, i.e. passes through it.

The nozzle 8 has an essentially cylindrical conformation; it comprises a substantially flared divergent proximal region 34 for the connection to the distal portion 4 of the body 2.

Moreover, the nozzle 8 comprises a convergent distal region 35, which defines the outflow port 36 from which the combustion products generated inside the burner 1 are adapted to flow out.

The first outlet section 13 and the second outlet section 15 are adapted to diffuse, respectively, the primary combustion air and the secondary combustion air inside the nozzle 8.

The first outlet section 13 and the second outlet section 15 are arranged on respective different planes with respect to the longitudinal axis A of the burner 1 (since the partition 23 exits from the body 2 by a certain length): therefore, the second outlet section 15 is further back with respect to the first outlet section 13, with reference to the direction of flow of the gases.

This represents an advantage inasmuch as the secondary air is mixed with the primary air after having covered a certain distance along the nozzle 8, so as to reduce as much as possible its influence on the possible generation of phenomena of turbulence.

The burner 1 comprises a first duct 37 for the supply of primary air; the first duct 37 ends in the first port 5.

Moreover, the burner 1 comprises a second duct 38 for the supply of secondary air; the second duct 38 ends in the second port 6.

According to another aspect of the invention, the burner 1 comprises a substantially Y-shaped fitting 39, for the (primary and secondary) air inlet in the burner 1.

The first duct 37 and the second duct 38, in practice, make up the two divergent branches of the aforementioned fitting 39.

The fitting 39 comprises an air inlet opening 39a.

More in detail, the first duct 37 has an orthogonal, or substantially orthogonal, axis to the longitudinal axis A of the burner 1.

The second duct 38, instead, has an inclined axis, by a certain angle, with respect to the longitudinal axis A of the burner, and therefore also with respect to the axis of the first duct 37.

The fitting 39 can be made in a single piece with the body 2, or it can be made as a separate element, associated with the body 2 with suitable connecting members.

According to one aspect of the invention, the first duct 37 comprises a corresponding first regulation device 40 for regulating the primary air flow rate. Moreover, the second duct 38 comprises a respective second regulation device 41 for regulating the secondary air flow rate.

The first regulation device 40 and the second regulation device 41 allow the primary and secondary air flow rates to be varied independently of one another. In a preferred embodiment of the invention, the first regulation device 40 can comprise a first butterfly valve 42.

Similarly, in a preferred embodiment of the invention, the second regulation device 41 may comprise a second butterfly valve 43.

The butterfly valve solution is very simple and economical in design, and at the same time effective and reliable.

The first butterfly valve 42 and the second butterfly valve 43 are controlled by respective first, second operating members 44, 45.

The first, second operating members 44, 45 are e.g. of the manual type. The first, second operating members 44, 45 comprise, for each of the butterfly valves 42, 43, a little arm 46 having an extremity locked together with the axis of rotation of the valve 42, 43 itself.

The little arm 46 is arranged orthogonally, or substantially orthogonally, to the aforementioned axis of rotation of the valve 42, 43; the extremity of the little arm 46 opposite that of connection to the axis of the valve 42, 43 has a knob 47, which is associated with the little arm 46 itself by means of threaded connecting members, which allow it to be screwed and unscrewed with respect to the little arm 46 itself.

For example, a threaded pin (not shown in the figures) is locked together with the end of the little arm 46, and can be engaged in a nut screw provided in the knob 47.

As shown in figure 2, the outer casing of the fitting 39 (or more generally of the body 2) comprises, for each of the regulation devices 40, 41, a respective slot 48, substantially shaped as an arc of circumference.

The center of the circumference along which the slot 48 extends belongs to the axis of rotation of the respective valve 42, 43.

For each of the butterfly valves 42, 43, the knob 47 is guided along the respective slot 48 in its rotation; more specifically, the threaded pin to which the knob 47 is connected is guided inside the respective slot 48; the knob 47 is then arranged outside the fitting 39 - or the housing of the body 2 - while the little arm 46 is inside it.

In order to block each butterfly valve 42, 43 in the respective desired position, and then regulate the primary and secondary air flow rate accordingly, it is necessary - after having determined the correct position of the knob 47 along the slot 48, which corresponds to a certain angular position of the respective butterfly valve 42, 43 - to screw the knob 47 along the respective pin, so that the knob 47 itself comes into contact with the external surface of the casing of the fitting 39, or more generally of the body 2: the friction generated is sufficient to withhold the butterfly valve 42, 43 in the preset position, so as to prevent accidental shifts.

It should be noticed that in the construction solution of the burner 1 shown in Figures 1, 2 the regulation devices 40, 41 have some slight differences with respect to those shown, on the other hand, in Figure 3: in particular, in Figures 1, 2 the two butterfly valves 42, 43 have their respective axes of rotation lying on the same plane, while in Figure 3 the two butterfly valves 42, 43 are arranged with their respective axes of rotation parallel.

The operation of the burner according to the invention is, in the light of what has been described, completely intuitive.

The combustion air is introduced through the inlet opening 39a of the fitting 39, and from here it continues towards the first duct 37 and the second duct 38. Through the first regulation device 40, or the second regulation device 41, it is then possible to determine, and then distribute, the air flow rates to be conveyed through the first duct 37 (primary air) and the second duct 38 (secondary air) respectively.

More in detail, the first duct 37 flows, through the first port 5, at the cage element 25; the primary air, therefore, flows through the first duct 37, reaches the cage element 25, passes through the openings 26 of the latter and is channeled along the partition 23.

The primary air consequently reaches the first diffuser 29, passes through it and its trajectory is consequently diverted, obtaining a turbine that facilitates mixing with the fuel.

The second duct 38 instead flows, through the second port 6, at the lateral surface of the partition 23.

The secondary air, therefore, after having crossed the second duct 38, is channeled into the gap 24 comprised between the inner surface of the body 2 and the outer surface of the partition 23; from here, the secondary air reaches the second diffuser 32, crosses it and its trajectory is consequently diverted, obtaining a turbine that facilitates mixing with the fuel.

Thanks to the characteristics of the burner 1 according to the invention - in particular the first passageway 12 of the primary air, the second passageway 14 of the secondary air, and the respective regulation devices 40, 41 - it is possible to obtain effects not achievable with burners of the known type currently in use. First of all, in situations where high thermal power is required, and therefore with a high combustible gas flow rate, a suitable distribution between primary and secondary air prevents the occurrence of unpleasant phenomena of turbulence inside the nozzle 8.

More in detail, the primary air flow rate can be regulated, i.e. limited, by means of the first regulation device 40, in such a way as not to exceed the maximum critical value beyond which phenomena of turbulence could be generated in the central area of the nozzle 8, in the proximity of the fuel outlet.

Additional air, required to obtain a combustion suitable to generate the required thermal power, can then be supplied through the second passageway 14, i.e., as secondary air, suitably regulated by means of the second regulation device 41. As previously explained, the secondary air flows through the second passageway 14 and crosses the second outlet section 15, which is arranged more externally than the first outlet section 13, and is therefore further away from the longitudinal axis A of the burner 1 : it, therefore, has a much lesser influence on the generation of turbulence in the central area of the nozzle 8.

This solution therefore permits reaching thermal powers not currently reachable with burners of known type.

In situations where, on the other hand, a low thermal power is required, and therefore a low combustible gas flow rate, the primary air flow rate is suitably limited, by means of the first regulation device 40, so as not to cause flame burn-out, and therefore the burner to shut down.

As a result of this, there is not enough primary air to obtain a combustion suitable to generate the required thermal power, even if minimal: therefore, in this situation as well, the secondary air, the flow rate of which is appropriately set through the second regulation device 41, is used to address the deficiencies due to the limitation of the primary air.

It follows that, thanks to this solution, the burner 1 can also operate smoothly, and therefore in a problem-free way, with thermal powers lower than those achievable by burners of the known and currently used type.

More generally, therefore, the use of secondary air in addition to primary air - with the respective flow rate adjustments set in relation to the specific situation of use - prevents the occurrence of undesirable phenomena of instability inside the nozzle 8, or other uncontrollable phenomena that can cause the accidental shutdown of the burner.

In other words, the burner behaves as if it were provided with an air diffuser with variable geometry, easily controllable by adjusting the flow rate of the primary and secondary air respectively.

By varying the ratio between the primary and secondary air flow rates, therefore, an effect is obtained similar to that which could be obtained by varying, hypothetically, the ratio between the external diameter of the first diffuser 29 and the external diameter of the second diffuser 32.

The primary and secondary air can be supplied at ambient temperature, or they can be - the one, the other or both - preheated to a certain temperature.

The results described above are obtained with a simple and economical construction solution, in which the regulation of the primary and secondary air flow rates is easy, precise and intuitive.

Another embodiment of the burner 1 according to the invention is shown in Figure 4, with some parts removed for greater clarity.

This embodiment differs from the previous one in terms of the shape of the first duct 37, for the supply of primary air, and of the second duct 38, for the supply of secondary air.

More in detail, in this embodiment, the first duct 37 and the second duct 38 are completely separated from each other, and do not originate from a single fitting as in the previous embodiment.

This solution permits - for example - using gases from different power sources as primary and secondary air respectively.

Always by way of example, the first duct 37 can be supplied with clean air, while the second duct 38 can be supplied with“dirty” or recycled air, coming from the same kiln/dryer or from other devices/systems.

This way - with reference to the gas supplied through the second duct 38 - the burner 1 behaves as a post-combustion device, with the possibility of abating certain harmful substances, such as, for example, volatile organic solvents, or VOCs, so as to improve emissions.

It has thus been seen that the invention achieves the intended objects. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

Furthermore, all the details may be replaced by other technically equivalent elements.

In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the following claims.