EP0549415A1 - Gas burner with combustion grid, combustion method and heating installation comprising such a burner - Google Patents

Abstract

Burner fed with oxidant air and with combustible gas, comprising a distribution chamber (3) which communicates with a combustion chamber (11), with a combustion grid (13) being interposed between them. The distribution chamber is fed tangentially with air and gas and comprises an agitating fan (15). The burner can be ignited via the periphery of the combustion chamber and allows air to be blown onto the ignition means (47) at the end of the ignition sequence. Such a burner can in particular be used on a compact submerged-tube heating installation. <IMAGE>

Description

the invention relates to a gas mixture burner and combustion grate (s), usable in particular on heating installations with submerged tube, or even on boxes for producing air or hot drying gas.

There are of course today many burners belonging to this category.

However, various practical difficulties remain linked in particular to problems of excessive heating in the flame catchment areas, of instability of the latter and of combustion quality liable to generate malfunctions and in particular excessive production of oxide of carbon, or even burner damage.

In particular in the context of submerged tube installations for heating industrial baths, the applicant has already proposed a few solutions, one of which is set out in French patent application FR-A-2 606 492 filed on November 7, 1986.

With a permanent aim of improvement, the applicant now proposes an improved combustion and heating installation making it possible to improve the conditions for mixing the gases to be burned, to limit the problems of thermal stresses, by ensuring combustion conditions favorable to a good attachment of the flames and limiting a priori the quantities of harmful gases emitted (in particular carbon and nitrogen oxides).

The solution proposed in the invention consists in particular in supplying air and gas tangentially to the distribution chamber of the burner where the combustion air and the combustible gas must be mixed and to have in this chamber a turbine promoting this air / gas mixture with induced effect conducive to good mechanical resistance over time of the main combustion grate usually interposed between said distribution chamber and the combustion chamber.

In this way, we will be able to ensure very efficient mixing of air and combustible gas, by promoting the attachment of the flames to the grid, which thus promotes resistance to thermal stresses, this inducing beneficial effects on the quality of combustion and therefore the limitation of harmful gases produced.

Advantageously, the stirring turbine will be placed facing this main grid, preferably substantially at the level where the distribution chamber is supplied with air and gas via a lateral pipe, so that the blades of the turbine receive transversely. the air and gas flow allowing them to enter into rotation naturally.

According to another characteristic of the invention, the distribution chamber will advantageously be surrounded by a peripheral ignition chamber making it possible to ensure ignition of the burner by the periphery of its combustion chamber.

As for the means of ignition and flame control usually required on this type of installation, we prefer to deport them away from the main grate, to mount them through a secondary combustion grate in the form of a frame or crown, interposed between the aforementioned peripheral ignition chamber and the burner combustion chamber.

To make the proportions of air and gas supplying the burner distribution chamber and the peripheral ignition chamber independent of each other, it has also appeared preferable to isolate these two chambers from one another by adding each with its own air and gas supply pipe.

• pour allumer le brûleur, on alimente sa chambre d'allumage périphérique en air et en gaz,
• puis, alors que le brûleur est allumé, on interrompt l'alimentation en gaz combustible de la chambre périphérique d'allumage, tout en maintenant son alimentation en air.

In addition to the burner which has just been presented, the invention also relates to a method of combustion of such a burner, this method being characterized essentially in that:

• to light the burner, we feed his room peripheral ignition in air and gas,
• then, while the burner is on, the fuel gas supply to the peripheral ignition chamber is interrupted, while maintaining its air supply.

With such an operating principle, we will of course again be able to limit the thermal stress problems by enveloping the burnt gases with an air film and by offering an effective solution to the problem of the thermal protection of the ignition and flame control.

The burner of the invention being very particularly usable on compact submerged tubes intended for the heating of industrial baths, the invention also relates to such a heating installation characterized in that it comprises a burner of the aforementioned type including the combustion chamber is connected to a heat exchanger tube immersed in the liquid bath to be heated.

• la figure 1 illustre schématiquement en vue de face un brûleur conforme à l'invention,
• la figure 2 est une vue de dessus du brûleur dans le sens de la flèche II de la figure 1, la turbine et ses éléments support ayant été retirés,
• la figure 3 montre en coupe transversale médiane un type de turbine utilisable dans le cadre de l'invention,
• et la figure 4 est une vue schématique partiellement en éclaté du brûleur de la figure 1 utilisé sur une installation de combustion à tube immergé compact.

In what follows, we will now provide a more detailed description of the invention, in relation to the appended drawings given solely by way of nonlimiting examples and in which:

• FIG. 1 schematically illustrates a front view of a burner according to the invention,
• FIG. 2 is a top view of the burner in the direction of arrow II in FIG. 1, the turbine and its support elements having been removed,
• FIG. 3 shows in median cross-section a type of turbine usable in the context of the invention,
• and Figure 4 is a schematic partially exploded view of the burner of Figure 1 used on a compact submerged tube combustion installation.

In Figures 1, 2 and 4 above, there is therefore illustrated a gas burner 1 of the general type with premix and combustion grate.

To ensure an efficient mixture of air and combustible gas which feeds it, this burner comprises a distribution chamber 3 (sometimes called the "premix" chamber).

This distribution chamber which may in particular have a cylindrical shape of substantially circular section is tangentially supplied with oxidizing air and combustible gas under pressure (preferably at least partially mixed already) via an intake manifold 5.

As can be seen more clearly in FIG. 2, the tube 5 can come from the main air supply pipe 7 to which the main fuel supply pipe 9 is connected, at the location of an elbow 7a (preferably last before room 3).

The connection at 9a of the pipe 9 can in particular take place just after a bend 9b, so that the combustible gas opens into the combustion air pipe substantially parallel to the axis 7b of its last rectilinear part forming the tube, with an end portion 9a formed in a bevel in the direction of the flowing flow.

In order to stabilize the flame front, the distribution chamber 3 is separated from the combustion chamber 11 by a flame attachment grid or so-called "main" combustion grid 13 disposed transversely between these two chambers.

In this case, the grid 13 has the shape of a circular disc perpendicular to the cylinder axis of the chamber 3.

It can be carried out in particular from materials and structures of the sintered bronze type or stack of finely perforated metal sheets or also of fibrous ceramic or metallic fabric, so as to advantageously have a incomplete structure, porous to the mixture of air and gas. which will then flow through the orifices or passages made through it.

To improve the quality of combustion and promote the mechanical strength (particularly in the face of thermal stresses) of this grate, we have arranged facing it, in the chamber 3, a stirring turbine 15. It appeared preferable to place this turbine substantially at the level of the zone, opposite the grid, where the lateral pipe 5 is tangentially connected to the chamber 3.

In this way, the blades 17 of the turbine (which can be seen more clearly in FIG. 3) will be able to receive the gaseous mixture transversely, forming a partition in the chamber.

A boss 19 situated, in FIG. 1, towards the top of the chamber 3 supports the rotation shaft 21 of the turbine which can rotate there in a conventional manner, via ball bearings (not shown).

It will be noted that, taking into account the tangential arrangement of the inlet 5, the turbine thus arranged will be able to be naturally rotated and quickly reach its optimum speed (for example of the order of 10,000 rpm) without any other drive device, thus ensuring a first homogenization of the mixture, the rotational movement of this turbine also generating recirculation currents between the upstream (AM) and the downstream (AV) giving this mixture very good homogeneity while 'it is blown axially towards the grid 13.

In Figure 3, there is shown in more detail the active part of a turbine which here consists essentially of two parallel plates 23, 25 extending perpendicular to the vertical axis of rotation 27 of the drive shaft 21 These two plates, which can have the shape of a disc, are separated by a series of mixing blades 17, so that the latter receive the flow to be brewed transversely (shown diagrammatically by the arrows 29), either directly or through orifices. distribution 31 formed in the upper plate, these orifices, as well as the large central orifice 33 formed in the lower plate 25, favoring the dynamics of the turbine and the recirculation movements of the flow.

For the ignition of the burner, the invention retained the solution of a "peripheral" ignition, via an ignition chamber 35 extending all around the distribution chamber 3, a priori essentially in its downstream part (AV) (see FIG. 1).

So as to be able to regulate at will and autonomously the air and the gas supplying respectively the distribution and ignition chambers, it appeared preferable to isolate them from each other by a partition 30 and d 'ensuring the ignition chamber 35 has its own mixture inlet, via a tangential supply pipe 37.

In practice, the pipe 37 may come from a tapping carried out at 37a on the main air supply pipe 7, of larger cross section, the combustible gas being able to be introduced into this pipe by a pipe with a further reduced section 39 originating therefrom. -even a tapping carried out on the main pipe 9 for supplying combustible gas, this tube 39 joining the tube 37 at the place of a penultimate elbow 37b, substantially under the same connection conditions as those mentioned for lines 9 and 7.

To ensure the metering of the mixture supplied to the ignition chamber 35, provision may be made to interpose a diaphragm 41 on the pipe 37 and an injector 43 on the pipe 39.

And for the attachment of the ignition flame, a secondary combustion grate 45 will advantageously be interposed between the ignition chamber and the combustion chamber 11.

The distribution chambers 3 and ignition 35 being preferably arranged concentrically, this secondary grid may in particular have the shape of a frame or of a crown surrounding the main grid.

Such an arrangement is advantageous.

Indeed, if the necessary ignition 47 and flame control means 49 are mounted in the chamber 35, in such a way that they pass through the grid 45, it will be possible not only to ensure efficient peripheral ignition, but also to improve control conditions by limiting the thermal stresses borne by these accessories. For this, it will suffice when the ignition sequence of the burner start-up cycle is completed and the latter is kept lit by flame detection, to cut off the gas supply to chamber 35 while maintaining its supply in the air.

The flames hung so far on the secondary grid 45 will therefore be extinguished. But the air coming from the pipe 37 will continue to escape through this grid towards the combustion chamber 11, this air flow then constituting an excellent means of continuous cooling of the spark plug 47 and of the control electrode 49, or even flanges 51 and 55.

In FIG. 2, the preferred locations of these ignition and flame control means are shown diagrammatically at 47a and 49a respectively, the position of which has intentionally been shifted by π / 2 in FIG. 1 so that they can be represented therein .

Note that the arrangement of Figure 2 is advantageous in that it allows first of all to deport said means 47, 49 away from the main grid 13, which is not crossed by any device, and in that that the gas / air mixture emerging from the pipe 37 by turning in the chamber 35 may thus first meet the ignition electrode and then the flame control electrode, with a certain logic of the sequences.

Of course, the secondary grid 45 may have a structure comparable to the main grid 13, that is to say a "porous" structure, for example consisting of the stacking of two rings of perforated sheet metal.

• a) Tout d'abord, les chambres de répartition et d'allumage avec leurs accessoires peuvent être portées par une platine support 51 permettant de fixer sur le brûleur un équipement complémentaire du type électrovanne, pressostats, transformateurs d'allumage...
  Cette platine peut venir coopérer de façon articulée en rotation via des éléments complémentaires de charnière 53a, 53b, avec une platine ou bride complémentaire 55 à laquelle est fixée la chambre de combustion 11, vers son entrée.
• b) Par ailleurs, un joint torique 57 interposé entre la platine 51 et la bride 55, à l'endroit d'un chanfrein conique usiné dans cette bride, pourra favoriser le centrage de la tête du brûleur sur la chambre de combustion, en diminuant les transferts thermiques par conduction provenant de cette chambre, assurant ainsi une relative isolation thermique des parois et accessoires de la tête du brûleur par absence de contacts directs entre les parties 51 et 55, sauf à l'endroit de leurs boulons de liaison.
  Toujours sur la figure 4, on pourra en outre remarquer que le brûleur est ici représenté monté sur une installation à tube immergé, la chambre de combustion 11 étant reliée en sortie à un tube échangeur de chaleur 59 (par exemple métallique) passant ou serpentant dans un bain 61 de liquide à chauffer, les produits de combustion étant ensuite évacués vers l'air libre par la sortie 63. Tant la chambre de combustion que le tube 59 sont immergés.

Referring to Figure 4, we can also note two characteristics that can conveniently complement the equipment of this burner:

• a) First, the distribution chambers and ignition with their accessories can be carried by a support plate 51 for fixing on the burner additional equipment of the solenoid valve type, pressure switches, ignition transformers ...
  This plate can come to cooperate in an articulated manner in rotation via complementary hinge elements 53a, 53b, with a complementary plate or flange 55 to which the combustion chamber 11 is fixed, towards its inlet.
• b) Furthermore, an O-ring 57 interposed between the plate 51 and the flange 55, at the location of a conical chamfer machined in this flange, may favor the centering of the burner head on the combustion chamber, by reducing heat transfers by conduction from this chamber, thus ensuring relative thermal insulation of the walls and accessories of the burner head by the absence of direct contacts between the parts 51 and 55, except at the location of their connecting bolts.
  Still in FIG. 4, it may further be noted that the burner is here shown mounted on a submerged tube installation, the combustion chamber 11 being connected at the outlet to a heat exchanger tube 59 (for example metallic) passing or snaking in a bath 61 of liquid to be heated, the combustion products then being evacuated to the open air by the outlet 63. Both the combustion chamber and the tube 59 are immersed.

Claims (9)

1 - Burner supplied with combustion air and combustible gas, comprising a distribution chamber (3) tangentially supplied with air and combustible gas and communicating with a combustion chamber (11), through a main transverse combustion grate (13) characterized in that said distribution chamber contains a turbine (15) which promotes the mixing of air and combustible gas and is conducive to the mechanical resistance over time of the grid. 2 - Burner according to claim 1 characterized in that the turbine (15) is arranged facing the main combustion grate (13), substantially at the level of a lateral zone of the distribution chamber (3) where the latter is tangentially supplied with air and combustible gas. 3 - Burner according to claim 1 or claim 2 characterized in that the distribution chamber (3) is supplied with air and combustible gas by a single lateral tube (5) extending axially the end part of a supply line in air (7) to which is connected, at a bend, last before the distribution chamber, a fuel gas supply line (9) opening into the air line, substantially parallel to said pipe ( 5). 4 - Burner according to one of claims 1 to 3 characterized in that the distribution chamber (3) is surrounded by an ignition chamber (35) which can be supplied with air and combustible gas for ignition of the burner and communicating with said combustion chamber (11) through a secondary combustion grate (45) in the form of a frame or crown surrounding said main grate and through which are mounted means (47, 49) for ignition and / or flame control, these means being thus deported away from the main grid and the distribution chamber. 5 - Burner according to claim 4 characterized in that the peripheral ignition chamber (35) is connected to a tangential gas supply pipe (37), said ignition (47) and flame control (49) means being angularly offset so that the flow rotating gas first meets the ignition means and then the flame control means. 6 - Burner according to any one of claims 4 or 5 characterized in that the ignition (35) and distribution (3) chambers are isolated from each other by a wall (30), with each of air and gas supply conduits (5, 37) which are connected thereto, so that their proportions of air and gas are independent from one chamber to another. 7 - Burner according to any one of claims 4 to 6 characterized in that a seal (57) interposed between the combustion chamber (11) and the distribution (3) and ignition (35) chambers provides a relative thermal insulation of the latter by limiting thermal transfers by conduction. 8 - Heating installation comprising a burner according to any one of the preceding claims, the combustion chamber (11) of which is connected to a heat exchanger tube (59) immersed in a bath (61) of liquid to be heated. 9 - Method of combustion of a burner according to any one of claims 4 to 7 characterized in that: - to light the burner, its peripheral ignition chamber (35) is supplied with air and combustible gas which is ignited by an electrode belonging to said ignition means (47), - Then, while the burner is lit, the fuel gas supply to the peripheral ignition chamber is interrupted, while maintaining its air supply.

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