EP1058052B1 - Liquid fuel burner with low NOx and dust emission and atomizer therefor - Google Patents

Description

The present invention relates to burners with liquid fuel and with low NO _x and dust emission, and atomizers (or sprayers) with liquid product for such burners.

The technical field of the invention is that of the manufacture of industrial liquid fuel burners (oil and fuel oil in particular).

Recent developments in liquid fuel burners have aimed to reduce pollutant emissions (unburnt carbon solids, CO, NO _x , O ₂ involved in the formation of SO ₃ ), while maintaining the operating performance of boilers, gas generators hot, incinerators, in particular the radiation of flames in the hearth, the dimensions of the hearths (therefore the flame dimensions), the possible charge variation, the absence of coke deposits or sediments on the tubes of the hearth, on the stabilizer of the burner, or on its refractory burner.

The technique of recirculating (or “recycling”) fumes with low O ₂ content in the combustion air of the burners, sometimes called FGR for “Flue Gas Recirculation”, the effect of which is on the one hand to reduce the concentration of O ₂ in the oxidizer, to promote the reduction of “combustible” NO _x and, on the other hand, to reduce the combustion temperature for the reduction of “thermal” NO _x formed by the oxidation of nitrogen in the oxidizer ( very sensitive to temperature), has its limits; it causes in particular a slowing down of the combustion process, and consequently an often unbearable increase in the length of the flames, as well as a significant increase in the emissions of unburnt carbonaceous solids, as well as CO and unburnt hydrocarbons.

The technique of globally staging combustion in running the burners in lack of air, then adding the air further downstream in the smoke circuit through openings (sometimes called "OFA ports" for "Over Firing Air"), also has its limits ; in fact, the quality of the mixture (air-combustion gas) obtained with such a process is weak, since the air injections on the walls cannot blend harmoniously throughout the vein of combustion gases and the result is insufficient performance in solid and gaseous unburnt matter, because the mixture is poorly organized; he would be better to organize this mixture at the level of each injection of fuel, i.e. at each burner.

Finally, the technique sometimes called “reburning” consisting in injecting a fuel, often gaseous, at the end of the furnace to reduce the NO _x to N, then adding the combustion air of the fuel at a later stage, is expensive and complicated, and in any event subject to a better final result if the NO _x have already been reduced to the minimum at each burner.

Consequently, the reduction of NO _x emissions, while keeping the emission rate of solid, gaseous unburnt and O ₂ as low as possible at each burner, is a necessity even if the FGR techniques, staging with OFA and reburning are used: there is interest in reducing pollutant emissions from the start of combustion, i.e. at the level of the heads (or canes) of the burner nozzle holders, even if additional overall reduction methods are employed.

Studies carried out on the reduction of NO _x (without significant increase in unburned) at the level of the burners, have highlighted the advantage of causing the separation of the flames into several elementary flames, in order to cause a fall in the emission of NO _x by several effects described in patent EP 0435735 (IFP-PILLARD).

The advantage of improving the separation of the flames while shortening each elementary flame by means of a stepped air injection targeting exactly each elementary flame has been highlighted, because it makes it possible to keep the diameters and lengths of flame unchanged, and d '' further improving the performance in terms of unburnt and level of reduction of NO _x , as described in US Patent 5,562,437 (PILLARD).

These improvements do not eliminate the need to improve atomization (or spraying) of liquid fuels, using a auxiliary atomizing fluid (saturated or superheated steam, air compressed, gas under pressure).

To this end, patent FR 2641365 proposes a burner comprising a primary spray part which delimits an axial mixing chamber into which the liquid fuel is introduced axially and radially or tangentially an auxiliary fluid under pressure; bedroom has primary spray nozzles each having a exit from which a jet of atomized fuel emerges; the burner has in addition to a secondary spray part which envelops the part primary spraying by delimiting with it an auxiliary chamber; the secondary part carries a plurality of secondary nozzles each of which is coaxial with a primary nozzle and has a diameter greater than the orifice of exit from it; the burner has means for injecting radially in the auxiliary chamber an auxiliary fluid under pressure sufficient for it to expand in the secondary nozzles, around the jets coming out of the primary nozzles, with an axial speed greater than the speed the peripheral layers of the sprayed fuel jets.

The burner head (or end) described in this document includes, in addition to the primary and secondary nozzle holder parts, several parts removable arranged between the nozzle holder parts and the body (of the cane) of the burner: an emulsifier defining a fuel mixing chamber and auxiliary fluid, which has passages (for auxiliary fluid) equipped with fins, as well as a diaphragm (or pellet) provided with an orifice central calibrated for the introduction of fuel into the mixture, and a fuel guiding part (sometimes called an atomizer) upstream of the diaphragm; these different pieces in the general shape of discs thick are "stacked face to face and secured to the burner head by a cap which surrounds them, which is screwed on the burner head and which has a shoulder leaning against the periphery of the nozzle holder part spray.

The object of the present invention is to provide burners, in particular such as those described in patent FR 97/09594 (PILLARD), that are improved.

An objective of the invention is to simplify the production of atomizers of liquid fuel, in particular those described in the patents FR 1305391 and FR 2641365, while keeping the functions unchanged and performance at least equal.

An objective of the invention is to allow the optimization of the Atomizer / burner “couple”, thanks to improvements concerning including the design of atomizers and removable rods atomization of liquid fuel and so the burner bodies themselves, to allow easy control of the optimization of this "Couple".

. To this end, the invention consists, according to a first aspect, in proposing a nozzle holder part capable of being removably mounted on a rod atomization of a liquid fuel burner, which comprises a connection in rotation with said rod, which member is preferably integrated to the structure of the nozzle-holder part to increase the solidity of the connection and make it possible to avoid any relative positioning defect in particular during frequent disassembly-reassembly operations for maintenance.

Thanks to this rotating link, the angle of orientation (trigonometric with respect to the axis of the burner) of the fuel jets liquid produced by the nozzle holder part can be adjusted to match precisely at the angular position of the secondary air injection nozzles. This allows in particular, in particular in the case of the burners illustrated Figure 2 of EP 774620 and US 5,562,437, to adjust and control the angular offset between the fuel injection port liquid and the position of the secondary nozzle, and which depends on the direction of "Rotation" printed by the burner with combustion air; the invention therefore allows to control the angular position of the room in which the liquid fuel outlet ports are drilled so that the angle orientation of the liquid fuel injection cane can be adjusted precisely, on a case-by-case basis, to optimize combustion.

According to a preferred embodiment of the nozzle-holder part, the latter has a cylindrical wall (hollow tubular) of circular section, which delimits a cylindrical cavity, which is extended and / or partially closed at one end by a transverse veil (or wall) thick (s) in which (which) are drilled holes forming the nozzles of fuel spray, and which is open at its second end: the latter is provided with a notch (or cutout) extending over a part of its circumference, for example half of it; this part end thus forms the connecting member in rotation, engaging with a small clearance in a cavity or depression of complementary geometry formed at the end of the rod receiving this removable nozzle holder piece.

Said cavity delimited by the cylindrical body of the nozzle-holder part, allows you to accommodate the other removable mounted parts on the rod of the burner which are used to form a jet of fuel, to mix it with the fluid auxiliary, as well as transporting and guiding the fluid and the fuel to the nozzles.

The removable attachment of the nozzle holder part to the rod can be carried out, as in patent FR 2641365, using a threaded sleeve (or nut) which surrounds the nozzle holder part while resting on the periphery of its front face, which is screwed to the end (threaded) of the rod of the burner.

Preferably said end of the nozzle holder part (or multi-nozzle) integrating the rotating connecting member, further comprises a connecting member in longitudinal translation adapted to cooperate with a complementary member provided at the end of the cane; this provision facilitates assembly and disassembly by allowing to hang (and / or hang) - cantilevered at the end of the rod - the nozzle holder part and the removable parts it contains, the common longitudinal axis of the rod and the nozzle-holder part being kept substantially horizontal; this allows the sleeve to be engaged around the multi-nozzle part without the hold, however it remains perfectly aligned and pressed against the end of the cane during this operation; preferably the organ of longitudinal connection and integrated into the multi-nozzle part and is presented under the form of a projection - such as a rib - provided on the internal face of the uncut part of said second end, which extends over a part of its circumference; the two integrated connecting members form thus a kind of hook capable of engaging in a circumferential groove corresponding provided at the end of the rod.

The advantages resulting from the nozzle-holder part according to the invention are moreover multiplied when, in accordance with a second aspect of the invention, a "complex" atomizer is used which integrates into a single part almost all of the functions usually performed by several pieces arranged end to end ("stacked").

Thus, according to another aspect, the invention consists in proposing a removable atomizer for fuel spray burner rod liquid, which has a longitudinal central opening (calibrated) for the fuel passage and several longitudinal peripheral orifices (for the passage of an auxiliary spraying fluid) leading to each end in an annular groove respectively provided on each face of the atomizer, each of said faces having grooves substantially radial; the atomizer, monobloc, further comprises on a face - called rear face - a depression surrounding said central orifice and into which tangential channels open, so that when the atomizer is mounted between the end of the cane and a nozzle holder piece (removable) by a sleeve-shaped fastener, the vacuum forms with the end of the rod an upstream rotation chamber fuel transported through these channels; the atomizer can if necessary have a second depression capable of delimiting with the nozzle holder part a mixing (emulsion) chamber; the atomizer features on a second face - called front face - of the radial or tangential channels which open around the central opening to allow mixing of the jet of fuel leaving the central orifice with the spray fluid.

In other words, the invention consists in proposing a part removable monobloc for liquid fuel burner rod, which includes means (comprising tangential injection channels and a tapered hollow face) for guiding the fuel flow allowing the formation of a conical jet at the outlet of a central orifice, means (longitudinal channels) for passage through the part of a fluid auxiliary and means (radial or tangential channels) for guiding the fluid downstream of the central orifice and allowing the fluid to come into contact with the fuel jet.

This one-piece piece can be accommodated easily thanks to its low thickness inside a housing (bore) provided in the nozzle holder part.

The advantages provided by the invention will be better understood from through the following description which refers to the accompanying drawings, which illustrate without any limiting character preferential modes of realization of the invention.

In the drawings, identical or similar elements bear, except otherwise indicated, the same references from one figure to another.

Figure 1 is a sectional view through a diametrical plane of a atomizer according to the invention.

Figures 2 and 3 are front views, respectively along II and according to III of the atomizer of Figure 1.

Figure 4 illustrates in sectional view through a diametrical plane a alternative embodiment of an atomizer according to the invention, which is shown between the end of a cane and the nozzle holder part (partially shown) that surrounds it.

Figures 5 and 10 illustrate in sectional view through a diametral plane the end of a cane fitted with an atomizer of figure 1 and a part multi-nozzle and a fixing sleeve; in figure 5 the parts are shown assembled while Figure 10 illustrates the separate parts and aligned.

Figures 6 to 8 illustrate three alternative embodiments of the groove circumferential fitted to the rod for temporary attachment of the part nozzle holder.

Figure 9 schematically illustrates in longitudinal section view a burner according to the invention equipped with sighting tubes for control visual of the orientation of the rod relative to the introduction orifices secondary air.

• deux ou plusieurs voies 9 tangentielles de mise en rotation du combustible liquide,
• une paroi plate ou conique 13 se terminant par un orifice 2 cylindrique ou conique de diamètre sensiblement inférieur au diamètre de sortie des voies 9 tangentielles, débouchant dans un volume 21, dénommé « chambre d'émulsion » ; ceci provoque la sortie du combustible .liquide sous la forme d'un voile conique par l'effet des vitesses générées par la pression du liquide ;
• deux ou plusieurs voies 8 radiales ou tangentielles permettant l'injection vers l'axe 20 du fluide FAA, avec un angle α de convergence de préférence compris entre 30 et 90° ; ces jets de FAA ont pour effet d'entrer en contact avec le cône de combustible liquide et de former, dans le volume 21, un mélange (FAA - combustible liquide) destiné à être injecté dans le foyer de combustion par un ou plusieurs orifices ou buses 22 reliant la chambre 21 au foyer 25 (figure 9).

The atomizer according to the invention (cf. FIGS. 1 to 5) consists of a single interchangeable part, of convex cylindrical external shape to facilitate installation in a cylindrical sheath; the atomizer 1 comprises an annular inlet 14 of liquid fuel CL surrounded by an annular inlet 5 of auxiliary atomizing fluid FAA (steam, air, gas under pressure) and includes various devices having complementary functions:

• two or more tangential ways 9 for rotating the liquid fuel,
• a flat or conical wall 13 ending in a cylindrical or conical orifice 2 of diameter substantially less than the outlet diameter of the tangential channels 9, opening into a volume 21, called "emulsion chamber"; this causes the liquid fuel to exit in the form of a conical veil by the effect of the speeds generated by the pressure of the liquid;
• two or more radial or tangential paths 8 allowing injection towards the axis 20 of the FAA fluid, with an angle α of convergence preferably between 30 and 90 °; these FAA jets have the effect of coming into contact with the cone of liquid fuel and of forming, in volume 21, a mixture (FAA - liquid fuel) intended to be injected into the combustion furnace through one or more orifices or nozzles 22 connecting the chamber 21 to the hearth 25 (Figure 9).

• on réduit les erreurs de montage par inversion d'ordre ou de sens comparé aux cannes comportant plusieurs pièces distinctes ; la pièce 1 peut être prévue avec une dissymétrie (un détrompeur) interdisant à l'opérateur de la monter à l'envers, en particulier si ses deux faces avant et arrière 6, 7 sont parallèles (α = 90°) ;
• le démontage est facilité ;
• le nombre de surfaces en contact est réduit à deux (au lieu de six surfaces pour trois pièces), ce qui réduit le nombre de risques de fuites de combustible liquide ou de FAA, et réduit quasiment à néant les risques de déformation des pièces de faible épaisseur ;
• le coût de fabrication est plus faible, puisqu'on économise quatre usinages de faces en contact et les gorges de liaison nécessaires ;
• les erreurs de choix de pièces parmi les stocks de rechange sont réduits ou annulés ;
• l'épaisseur totale de la pièce unique est nettement plus faible que le cumul des épaisseurs de trois pièces ; ce gain d'épaisseur présente de nombreux avantages induits : le fourreau cylindrique 23 appelé « écrou de blocage est plus court, plus facile à refroidir, plus solide, et sa longueur soumise à dilatation différentielle est réduite ; la pièce 19 de sortie percée d'orifices 22 est plus rapprochée de la pièce fixe 18 solidaire de la canne, ce qui permet de lier en rotation la canne 18 et la pièce 19 de sortie.

The advantages are:

• assembly errors are reduced by reversal of order or direction compared to rods comprising several distinct parts; the part 1 can be provided with an asymmetry (a key) preventing the operator from mounting it upside down, in particular if its two front and rear faces 6, 7 are parallel (α = 90 °);
• disassembly is facilitated;
• the number of surfaces in contact is reduced to two (instead of six surfaces for three parts), which reduces the number of risks of leakage of liquid fuel or FAA, and almost reduces to zero the risks of deformation of the parts of weak thickness ;
• the manufacturing cost is lower, since it saves four machining of faces in contact and the necessary connection grooves;
• errors in the choice of parts among the spare stocks are reduced or canceled;
• the total thickness of the single piece is significantly lower than the sum of the thicknesses of three pieces; this gain in thickness has many induced advantages: the cylindrical sheath 23 called “locking nut is shorter, easier to cool, more solid, and its length subjected to differential expansion is reduced; the output part 19 pierced with orifices 22 is closer to the fixed part 18 secured to the rod, which makes it possible to link the rod 18 and the output part 19 in rotation.

The removable monobloc atomizer 1 comprises (FIGS. 1 to 3) the orifice 2 longitudinal center for the passage of fuel and several orifices 3 longitudinal devices for the passage of a spraying fluid; it further comprises on each face 6, 7 a depression 10, 11 surrounding said central orifice, and a curved section 12 which makes it possible to engage it in a one-piece nozzle holder housing without risk of jamming and promotes its tightening against the end of the rod without risk of occurrence mechanical stresses likely to deform it, and further facilitates its plating to form a tight connection.

The central opening 2 is surrounded on a first face (rear) by a frustoconical surface 13 contributing to delimit the first depression 11, said first face 7 further comprising an annular groove 14 in which open the tangential grooves 9 of axis 9a, and comprising a annular rib 15 separating a groove 5 into which the orifices 3, of said groove 14 which it surrounds.

The orifice 2 is surrounded on the front face 6 of the atomizer, with a flat surface 16 perpendicular to the axis 20 and a cylindrical surface 17 parallel to axis 20, these two surfaces contributing to delimit a depression 10 (Figure 1).

On the front face 6, grooves or channels 8 with a radial axis 8a (FIG. 3), or alternatively tangential in another configuration not shown, connect the peripheral annular groove 4 into which the 3 longitudinal FAA transport channels open out with a central zone 10 of the face 6, if necessary in depression, which surrounds hole 2.

The part 19 removable nozzle holder (FIGS. 5 and 10) comprises several spray nozzles 22, and comprises a cylindrical housing 19a, with an axis 20, suitable for receiving the atomizer 1; the part 19 further comprises means indexing in rotation with the burner rod: for this purpose the end 19b open of the body is laminated or cut on a portion 19c of its circumference, so that the end portion is able to engage in a corresponding peripheral cutout 35 provided at the end of the rod 18 intended to receive the part 19, to form an angular stop.

The end part has a rib 19d on its face internal circumference which is able to engage in a groove 36 circumferential provided at the end of the rod to form an organ hooking allowing the suspension of the piece to the rod before their assembly by a sleeve 23 surrounding the part 19.

The liquid fuel burner rod 42 illustrated in FIG. 5 includes an atomizer 1 housed in the longitudinal bore 19a provided in the piece 19 nozzle holder; a removable sleeve 23 screwed onto the fixed part 18, surrounds and fixes the nozzle-holder part and the atomizer at the end 18 of the cane.

The liquid fuel burner 41 illustrated in FIG. 9 has a cane 42 according to the invention and means allowing the rotation of the cane relative to the opening 40 along the longitudinal axis 20 of the rod, which means comprising deformable connections (flexible, rotating or articulated) on the fuel and fluid supply lines spraying aid; these means are provided in the rear part 42a of cane 42.

The rod extends through an opening 40 and is equipped with nozzles 22 spray; the burner has several orifices 51 for injection of air and includes means for visual control of the angular orientation relative nozzles (and / or corresponding flames) and orifices oxidizer injection; these means include sight tubes 43 extending parallel to the rod in the extension of the orifices 51, at through the opening, fitted at their rear end (external to the hearth) with a sight 44 (or ocular).

Claims (11)

1. Liquid-fuel burner subassembly (42), which comprises:

   an end-piece (18) or head that is connected to a fuel feed duct (CL) and to an auxiliary fluid spray feed duct (FAA);

   a removable atomizer (1), which has fuel guiding means allowing the formation of a jet at the exit of a central orifice (2), and also longitudinal peripheral channels (3) for passage of the said auxiliary fluid;

   a removable nozzle holder (19) having several spray nozzles (22); and

   a removable sleeve (23), which surrounds the said nozzle holder (19) and the atomizer (1) and fastens these to the said end-piece (18);

   characterized in that the said atomizer is made of one piece and includes means (8) for guiding the said auxiliary fluid, allowing the fluid to be brought into contact with the said fuel jet downstream of the central orifice, and in that the said nozzle holder (19) furthermore includes means (19b, 19c) for rotational linkage with the said end-piece (18) of the subassembly, in order to form an angular stop.
2. Burner subassembly (42) according to Claim 1, in which the said nozzle holder includes a housing (19a) for housing the said atomizer (1).
3. Burner subassembly (42) according to Claim 1 or 2, in which the said nozzle holder includes a catching member (19d), allowing the said holder (19) to be suspended from the subassembly before they are joined together by the said sleeve (23).
4. Burner subassembly according to any one of Claims 1 to 3, in which the open end (19b) of the body of the nozzle holder (19) is cut along a portion (19c) of its circumference, in such a way that the end part can engage in a corresponding peripheral recess (35) provided on the end of the end-piece (18) intended to house the piece (19), in order to form the said angular stop.
5. Burner subassembly (42) according to any one of Claims 1 to 4, in which the end (19b) of the said nozzle holder (19) has, in addition to an integrated rotational linkage member forming an angular stop, an integrated longitudinal translation linkage member that can cooperate with a complementary member provided on the end (18) of the subassembly, the said two integrated linkage members forming a kind of hook, allowing the said piece (19) to be suspended from the subassembly before they are joined together by the said sleeve (23).
6. Burner subassembly according to any,one of Claims 2 to 5, the end part of the nozzle holder (19) of which has a rib (19d) on its internal circumferential face (36), which rib can engage in a circumferential groove provided on the end of the subassembly in order to form the said catching member.
7. Burner subassembly (42) according to any one of Claims 1 to 6, in which the said one-piece atomizer (1) comprises:

   a first face (7) having a frustoconical surface (13) surrounding the central orifice (2) and contributing to defining a depression (11), the said face (7) furthermore having an annular groove (14), into which annular groove tangential grooves (9) run, and an annular rib (15) separating an annular groove (5) into which the orifices (3), of the said annular groove (14) that surrounds it, run; and

   a second face (6) having an annular groove (4) into which the orifices (3) run, and also grooves (8) for passage of the said fluid as far as a central region (10) into which the central orifice (2) runs.
8. Burner subassembly (42) according to Claim 7, in which the grooves (8) are radial or tangential.
9. Liquid-fuel burner (41), characterized in that it comprises a subassembly (42) according to any one of Claims 1 to 8 and means that allow the subassembly to rotate relative to the quarl (40), which means include deformable (flexible, rotary or articulated) couplers on the feed ducts for the fuel and for the auxiliary spray fluid.
10. Liquid-fuel burner according to Claim 9, comprising a subassembly extending through a quarl (40) and equipped with spray nozzles (22), and having several fuel injection orifices around the subassembly, which furthermore includes means for visually checking the relative angular orientation of the nozzles and/or of the corresponding flames and of the oxidizer injection orifices.
11. Burner according to Claim 10, in which the visual checking means comprise a sighting tube (43) lying parallel to the subassembly through the quarl.

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