WO2010073156A1

WO2010073156A1 - A combustion head and a burner comprising the head

Info

Publication number: WO2010073156A1
Application number: PCT/IB2009/055419
Authority: WO
Inventors: Daniele Tagliazucchi
Original assignee: Tck - Societa' A Responsabilita' Limitata
Priority date: 2008-12-23
Filing date: 2009-11-30
Publication date: 2010-07-01
Also published as: ITMO20080329A1

Abstract

A mixer head for burners comprises a cylindrical and internally hollow main body (2) developing about an axis (3) and comprising a cylindrical lateral surface (4) delimited by an open end (2a), for enabling ingress of a gas into the cylindrical body (2) and by a closed end (2b), opposite the first end (2a). The cylindrical surface (4) exhibits a flame-igniting zone comprising a plurality of nozzles (5) for outlet of a gas. A flange (6) is located in proximity of the open end (2a) of the main body (2). The flange (6) comprises a plurality of slits (9) which allow a flow of air to cross the flange (6) and arrive in proximity of the nozzles (5). A cylindrical wall (12) is located about the diffuser disc (6) and the main body (2) in order to define therewith a mixing chamber (22).

Description

Description A Combustion Head and a Burner comprising the Head.

The invention relates to a combustion head, in particular for flame burners.

A flame burner for industrial kilns also forms part of the present invention, comprising the combustion head.

In particular, the combustion head of the present invention is preferably used in burners in kilns for firing ceramic materials (such as for example tiles) basins, sanitary appliances and furnaces for heat treatment of materials, especially metals.

Combustion heads in the prior art exhibit a cylindrical main body, internally hollow, having a small axial extension which is variable between 20 and 30 mm.

The inside of the main body is in fluid communication, via a first open end thereof, with a conduit of the burner, through which gas flows.

The opposite end of the main body is closed.

Nozzles are present on the lateral surface of the main body, arranged along a single circumference.

The gas exits through the nozzles.

A flange is located between the circumference containing the nozzles and the first end of the main body, which flange has a plurality of slits which cross it axially and place the two opposite sides of the flange in fluid communication. In other words, the flange has the appearance of a disc having a plurality of blades, through which the air flows. The flange is in fluid communication with a second conduit of the burner, preferably concentric to the conduit containing gas, through which the air flows. The air passes from this conduit through the slits between the blades to the base surface of the flange facing towards the nozzles. Here the air mixes with the gas exiting the nozzles.

To improve the mixture, the slits are generally inclined with respect to the axis of the main body, such as to give a swirling motion to the air.

The burner conduits, internally of which gas and air flow, are generally positioned externally of the kiln.

The combustion head, on the other hand, is contained in a portion of the burner which is inserted in the kiln wall, hi particular, the portion of the main body containing the nozzles faces towards the inside of the kiln, such that the flame zone is closer to the firing zone.

The applicant has noticed that these combustion heads, or similar heads, exhibit some drawbacks. In particular, the applicant has observed that the combustion heads of the prior art are susceptible to improvement from the point of view of the air-gas mixture.

The gas which flows internally of the main body exits radially from the nozzles at a considerable velocity, forming a sort of annular barrier to the axial air flow crossing the flange.

Thus, in order to improve mixing, it is often necessary to employ an air flow that is greater than the flow actually necessary for overcoming the counter-pressure created by the gas flow exiting the nozzles.

The combustion head of the prior art also has a high consumption of gas.

In this context, the technical task at the basis of the present invention is to provide a combustion head which obviates the drawbacks in the prior art as mentioned herein above.

In particular, an aim of the present invention is to make available a combustion head which improves the performance and combustion, leading to a reduction in gas consumption and a reduction also in the volumes of polluting substances.

A further aims is to provide a combustion head which, with a like gas flow, reduces the combustion air flow. A further aim of the present invention is to provide a combustion head which can accelerate the expulsion of fumes from the combustion chamber.

Finally, an aim of the present invention is to provide a combustion head which enables combustion to be improved such as to reduce breakage phenomena in the combustion chambers. These aims and other advantages are attained by the invention as it is described in one or more of the appended claims.

The set technical task and the set aims are substantially attained by a combustion head, comprising the technical characteristics set out in one or more of the accompanying claims. Further characteristics and advantages of the present invention will better emerge from the detailed description that follows, provided by way of non- limiting example, of a preferred though not exclusive embodiment of a combustion head, as illustrated in the accompanying figures of the drawings, in which: figure 1 is a schematic view in lateral section of a combustion head in a first embodiment of the present invention; figure 2 is a perspective view, partially sectioned, of a combustion head in a second embodiment of the invention; figure 3 is a plan view of the head represented in figure 2; figure 4 illustrates an axial section of a burner for industrial kilns comprising a mixing head of the present invention.

With reference to the figures of the drawings, 1 denotes in its entirety a mixer head of the present invention. - A -

The mixer head 1 for burners comprises a main body 2, preferably cylindrical, internally hollow and developing prevalently along an axis 3.

The main body 2 comprises an open first end 2a for allowing ingress of a gas and a closed second end 2b, opposite the first end 2a, which can also be open in other use conditions.

The main body 2 also comprises a lateral surface 4, delimited by two ends

2a and 2b, which exhibits a flame ignition zone comprising a plurality of nozzles or holes 5 for exit of the gas.

The nozzles or holes 5 have a diameter which varies between 0.5 mm and 5 mm, preferably between 1.5 mm and 2.5 mm, and are distributed on the lateral surface 4, an axial development of which is greater than the transversal dimension of the main body 2,

The head 1 exhibits a diffuser disc 6, or rosette, in proximity of the first end

2a of the main body 2, in particular between the nozzles or holes 5 and the first end 2a. The diffuser disc 6, coaxial to the main body 2, comprises a first base surface 7 facing towards the open end 2a of the main body 2,and a second base surface 8, opposite the first, facing towards the closed end 2b of the main body 2.

The diffuser disc 6 normally has a diameter comprised between 40 and 90 mm, preferably 57 mm and a thickness comprised between 3 mm and 50 mm, normally about 10 mm.

A peripheral annular portion of the diffuser disc 6 exhibits a plurality of slits 9, which place the first base surface 7 in fluid communication with the second base surface 8 of the diffuser disc 6. In other words, the diffuser disc 6 exhibits a sort of plurality of blades 10, intervalled by a plurality of slits 9 between which air flows. Normally the number of blades 10 does not exceed ten units. The slits 9 are advantageously inclined with respect to the longitudinal axis 3 of the main body 2, such as to give the air a swirling motion which improves the mixing thereof with the gas.

The slits 9 are preferably inclined with respect to the axis 3 by an angle comprised between 5° and 40°, preferably 30°.

The radial depth of the slits 9 almost covers the whole circular crown- section of the diffuser disc 6.

There is usually present an ignition element 11 on the second surface 8 of the diffuser disc 6, which extends towards the flame ignition zone. The ignition element 11 comprises, for example, a metal electrode which is electrically excited such as to create a spark which sets off the combustion of the mixture. The mixer head further comprises a flame detector, not illustrated in the figures of the drawings, which detects and signals the presence of a flame in the burner. The main body 2 has an axial development (projecting part with respect to the diffuser disc 6) comprised between 20 mm and 100 mm, preferably between 40 mm and 60 mm. The flame ignition zone, along which the nozzles 5 are distributed, has a length which is variable between 20 mm and 100 mm, preferably between 50 mm and 60 mm. The head 1 further comprises a cylindrical wall 12, positioned about the diffuser disc 6 and the main body 2. In particular, the cylindrical wall 12 exhibits an internal diameter equal to the external diameter of the diffuser disc 6, such that the cylindrical wall 12 is keyed directly on the diffuser disc 6. Together with the diffuser disc 6 and the main body 2, the cylindrical wall 12 defines a mixer chamber 22.

Internally of the chamber 22, the air in inlet from the slits 9 of the diffuser disc 6 mixes with the gas exiting from the nozzles or holes 5. The cylindrical wall 12 extends for about the whole axial length of the cylindrical body 2.

In a first configuration, illustrated in figure 1, the nozzles or holes 5 are aligned along at least a straight generatrix 13, parallel to the axis 3 of the main body 2. There are preferably present from two to eight straight generatrices 13, along which the nozzles or holes 5 are aligned, each made up with a number of nozzles 5 which varies from two to ten. Alternatively, as illustrated in figure 2, the nozzles 5 are arranged along at least a spiral line 14 winding about the cylindrical surface 4 of the main body 2.

There can be from two to ten spiral lines 14, preferably four. These spiral lines 14 can have a right- or left-wise direction and be in a same direction or a different direction to the inclination of the slits 9 of the flanges 6. Among the possible configurations are those which comprise nozzles or holes 5 arranged along spiral lines 14 that are different to the inclination of the slits 9, as these enhance air-gas mixture.

A further arrangement enhancing the mixture is one which includes a staggered distribution of the nozzles or holes 5 along the generatrices of the first illustrated embodiment or along the spiral lines of the second embodiment, i.e. a distribution thanks to which in a same section perpendicular to the axis 3 there is one nozzle or hole 5 alone (or there is a smaller number than the number of existing rows or generatrices). A burner 15 for industrial kilns comprises a first portion 16 which can be positioned externally of a kiln, in particular abutting against the external surface 17 of a wall 18 of the MIn. The burner 15 further comprises a second portion 19, aligned coaxially to the first portion 16, which is positionable internally of the kiln wall 18. The mixer head 1 as previously described is located internally of the second portion 19, with the flame zone facing towards the inside of the kiln.

The second portion 19 comprises a containing wall 19a. The mixer head 1 is preferably located internally of the burner 15, in such a position as to leave a passage hole 23 for the air between the inside of the cylindrical wall 19a and the cylindrical wall 12.

The first portion 16 and the second portion 19 are axially aligned and preferably cylindrical. The first portion 16 comprises a first conduit 20 and a second conduit 21 which are concentric and respectively supplied with gas and air. The first conduit 20 is in fluid communication with the open end 2a of the main body 2 of the mixer head 1, such that the gas. crossing the first conduit and entering the main body 2, exits from the nozzles or holes 5. The second conduit 21 is in fluid communication with the diffuser disc 6 of the mixer head 1; in particular, the air which crosses the second conduit 21 flows from the first surface 7 of the diffuser 6 and to the second surface 8 of the flange through the slits 9.

The slits impart a swirling motion on the air, thus improving the mixing thereof with the gas exiting the nozzles 5.

The invention offers important advantages.

The presence of the annular mixer chamber creates a zone internally of which the air mixes in an optimal ratio.

The air-gas mixture is also more uniform and happens in a dimensionally well-controlled zone. This contributes to the improvement of the combustion, with a consequent significant reduction of consumption, fume volumes to the chimney and pollutants. The velocity of expulsion of the fumes from the combustion chamber is also improved.

With a like-for-like flow of inlet gas, the presence of a large number of nozzles or holes distributed over a wide area developing coaxially of the flow enables the gas to be distributed more uniformly along the flame ignition zone and to exit from each nozzle or hole 5 at a relatively low velocity. In this way the gas jets do not form a barrier to the air flow and a better air-gas mixture is achieved, which considerably reduces (by about 15%) the quantity of combustion air at present necessary in burners installed in kilns of the prior art.

The mixer head of the present invention further enables saving gas in a case in which there is a pause in operations in the kiln, i.e. when there is a brief period in the kiln when there is no material to be fired. During this time, the burner remains lit without there being anything in the kiln to absorb the heat produced. Consequently, there is an accumulation of heat in the kiln and a change in the temperature profile from the desired curve. The present mixer head enables the burner to be kept on even with a minimum gas pressure of 2/3 mm H₂O, leading to savings of 3-5% in gas per day. Finally, the combustion chamber has a longer working life since there is less heating of the external wall of the kiln due to the fact that the nozzles or holes, and thus the flame zone, have a uniform and controlled longitudinal distribution internally of the combustion chamber. The bypass air flow, which passes through the hole afforded between the containing wall of the second portion of the burner and the cylindrical wall of the head, also enables the temperature of the external wall of the kiln to be reduced.

Claims

Claims.

1. A mixer head for burners comprising: a main body (2), cylindrical and internally hollow, developing about an axis (3), comprising an open first end (2a) for enabling inlet of a gas, a second end (2b), preferably closed, opposite the first end (2a), and a lateral surface (4), delimited by the first end (2a) and the second end (2b), exhibiting a flame-igniting zone comprising a plurality of nozzles or holes (5) for outlet of a gas; a diffuser disc (6), coaxial to the main body (2) and positioned in proximity of the open first end (2a) of the main body (2), comprising an annular peripheral portion provided with a plurality of slits (9) which place a first base surface (7) of the diffuser disc (6) in fluid communication with a second base surface (8) thereof located opposite the first base surface (7), for enabling passage of air; the slits (9) being inclined with respect to the axis (3) such as to impose a swirling motion on the air, an ignition element (11), characterised in that it comprises a cylindrical wall (12) located about the diffuser disc (6) and the main body (2), such as to define a mixing chamber together with the diffuser disc (6) and the main body (2).

2. The mixer head of claim 1, characterised in that the cylindrical wall (12) extends for about a whole axial length of the main body (2).

3. The mixer head of one of the preceding claims, characterised in that the plurality of nozzles or holes (5) are distributed on the lateral surface (4), a development of the lateral surface (4) in an axial direction being greater than a transversal dimension of the main body (2).

4. The mixer head of one of the preceding claims, characterised in that the plurality of nozzles or holes (5) are axially aligned along a plurality of generatrices (13) of the cylindrical lateral surface (4) of the main body (2).

5. The mixer head of one of the preceding claims, characterised in that the plurality of nozzles or holes (5) are aligned along a plurality of lines (14) which develop in a spiral fashion about the axis (3) of the main body (2).

6. The mixer head of one of the preceding claims, characterised in that the slits (9) are inclined with respect to the axis (3) of the main body (2) by an angle comprised between 10° and 40°, preferably 30°.

7. The mixer head of any one of the preceding claims, characterised in that the flame ignition zone of the cylindrical lateral surface (4) has a length which is comprised between 20 mm and 100 mm, preferably 50 mm.

8. A burner for industrial kilns comprising a first portion (16) which is positionable externally of a furnace and a second portion (19), coaxially aligned to the first portion (16), which is positionable internally of a wall (18) of the kiln, characterised in that the second portion (19) internally comprises a mixer head (1) according to one or more of claims from 1 to 7.

9. The burner of claim 8, characterised in that the second portion (19) comprises a containment wall (19a); the burner comprising a passage hole (23) between the mixer head (1) and an inside of the cylindrical wall (19a) for passage of air.

10. The burner of claim 8 or 9, characterised in that the first portion (16) comprises a first conduit (20) and a second conduit (21) which are concentric and are supplied respectively by gas and by air.

11. The burner of claim 10, characterised in that the first conduit (20) is in fluid communication with the open end (2a) of the main body (2) of the mixer head (1), such that the gas flows from the first conduit (20) internally of the main body (2) of the mixer head (1) and exits from the nozzles or holes (5).

12. The burner of claim 11, characterised in that the second portion (19) is in fluid communication with the diffuser disc (6) of the mixer head (1), such that the air flows from the second portion (19) to the second surface (8) of the diffuser (6) through the slits (9), in order to mix with the gas exiting from the nozzles or holes (5).