FR2780488A1 - IMPROVEMENT TO COMBUSTION APPLIANCES COMPRISING SEVERAL FUEL TRANSPORT DUCTS - Google Patents

Abstract

The present invention relates to an improvement made to combustion appliances comprising several conduits for transporting oxidant. The technical sector of the invention is the field of manufacturing combustion appliances with burners, such as boilers, gas generators. According to the present invention, a combustion appliance (1) comprises at least one burner (6) associated with two conduits (11, 12) for transporting gaseous oxidant, and comprises two registers (19, 21) sliding cylindrical.

Description

Improvement to combustion appliances with several flues

  transport of oxidant The present invention relates to an improvement made to combustion appliances comprising several conduits for transporting oxidant. The technical sector of the invention is the field of manufacturing combustion apparatus with burners, such as boilers, hot gas generators, ovens or the like. The present invention applies to combustion apparatuses using one or more solid and / or powdery, or fluid fuels, which comprise at least one burner associated with at least

  two coaxial ducts for transporting gaseous oxidant.

  The present invention applies in particular to installations for cogeneration of electrical and thermal energy in which exhaust gases from engines or turbines are heated by one or more burners, being used as oxidant, then are

  used to produce steam, hot water or hot gases.

  The object of the present invention is to propose an improved system for adjusting the flow of oxidant delivered to the burners; the present invention applies to burners equipped with several oxidant circuits or conduits; in such installations, a central conduit conveys a current of oxidizer generally said to be primary, which surrounds the nose of the burner and extends coaxially thereto; one or more other annular section conduits extend around the central conduit and transport a flow or stream of said oxidant

  secondary and where appropriate tertiary.

  The combination of these different oxidant streams, the speed and orientation of the resulting oxidant jets, exiting into the combustion chamber, must be kept within predetermined limits, makes it possible to produce efficient combustion installations, and makes it possible to control combustion, in particular the shape and stability of the flame, as well as the content of the various combustion residues, in particular the residues of formula Nox, CO

  whose training must be limited.

  It is generally intended to regulate the flow rate of oxidant circulating in a duct using one or more pivoting registers, for example essentially constituted by a plane flap pivoting along a central axis contained in the plane of the flap; this type of register has drawbacks, in particular with regard to its dimensions which are high having regard to the permissible oxidizer flow rate, and its poor performance in terms of stability and linearity; moreover, these registers do not lend themselves well to the installation in parallel of several registers, in order to regulate a flow of gaseous oxidizer.

important and variable.

  The object of the present invention is to provide a combustion appliance equipped with an improved system for adjusting the flow of

oxidizer.

  The invention consists in providing a combustion appliance which comprises at least one burner associated with at least two conduits for transporting gaseous oxidant, which comprises at least two sliding cylindrical registers, to allow independent adjustment of the respective flow of oxidant admitted by annular openings and / or arranged annularly in each of said oxidant transport conduits. Preferably, said cylindrical registers are coaxial, mounted to slide along their common longitudinal axis, and are of

different diameter.

  Thanks to the presence of at least two registers, the adjustment of the flow rate of oxidant circulating and / or admitted into the conduits can, on the one hand, be carried out independently for each conduit in order to maintain injection speeds of oxidant in the chamber combustion at predetermined values, and can moreover be carried out more precisely, over a greater range of variation of the flow rate, and with

  variable oxidizer supply pressures.

  Thanks to the cylindrical shape of the registers and the annular shape or arrangement of the inlet orifices of said conduits which they can completely or partially block, it is possible to obtain in the conduits a uniform distribution of the speeds and / or of the oxidant flows, and5 consequently obtain a homogeneous injection, according to a symmetry of revolution around the axis common to the registers and the conduits, of the different oxidant streams entering the combustion chamber, and this even when the oxidant (s) are delivered upstream of the registers by a non-coaxial conduit, in particular by a radial or oblique conduit (by reference to said axis of symmetry); these results are particularly easy to obtain using an assembly

  simple mechanical, robust, and stable in all the adjustment positions, by providing registers in the form of coaxial cylindrical ferrules sliding along their common axis, which allow to ensure a homogeneous flow in the oxidizer conduits, downstream of the registers, whatever whatever the degree of openness of the registers.

  By providing sliding cylindrical registers of different diameters, it is easy to obtain a structure which, while being compact, allows the flow of a high flow (or current) of oxidizer, thanks to the larger diameter of the external register and the large passage section that can be closed; this structure is in

  in addition particularly suitable for the equipment of burners, each equipped with two or three coaxial conduits for transporting oxidant, intended to deliver - by nozzles or flaps - balanced, axial, convergent or divergent, possibly rotating, oxidant jets25 in the combustion chamber.

  The compactness of the assembly can in particular be optimized by providing for a crossover (or overlapping or superposition) of the registers and / or of their support, guide and drive mechanism in translation, for certain open positions; in particular, this covering can take place in the open position of

  two registers whose directions of opening movements are opposite.

  The compactness of the assembly associating two or three registers (equipping two or three oxidizer conduits associated with a burner) is in particular optimized by providing registers whose diameters are such that the ratio of the diameter of the external register to the diameter of the internal register is smaller or equal to 2 (and greater than 1 except in certain cases where the diameters are substantially identical), in

  particular of the order of 1.3 to 1.6.

  By diameter is meant the equivalent diameters of the transverse profile of the register, in the case where the cross section of the oxidizer conduits and their associated registers is not in shape

  circular, but for example square or rectangular.

  Another advantage provided by the invention is that it makes it possible, in a combustion appliance equipped with two (at least) burners supplied with oxidizer by a single duct, to adjust easily, precisely and stably, generally at an identical value in the case of identical burners, the oxidant flow delivered to each duct of each burner, and therefore makes it possible to solve the difficulties inherent in such a balancing of the oxidant flows regulated by

registers arranged in parallel.

  According to a preferred embodiment, at least one of the registers is provided with sealing means, in particular means preventing the passage of oxidant in the closed position of the register (and / or limiting as much as possible the "leakage" flow rate in this position); these sealing means preferably comprise a crown or flange linked (or fixed) to the register, for example forming an integral part thereof, at a longitudinal end of the register; this crown is capable of coming substantially into contact with a (or pressing on) a fixed crown (or flange) forming part of the structure of the device, in the closed position of the damper, to close the passage to the downstream conduit oxidizer; these sealing means may include a deformable metal seal; this metal seal may comprise or be constituted by said flat crown fixed to the register and extending in a transverse plane (by reference to the longitudinal axis of symmetry of the register); by producing this crown in a thin sheet, in particular of the order of 0.5 to 2 millimeters, this crown can be deformed slightly by pressing on the fixed crown of the structure, which makes it possible to ensure the contact of the other end of the register, over its entire perimeter, with a second fixed wall or crown of the device, which consequently makes it possible to ensure a substantially sealed closure of the register by circumferential contact of its two ends

  longitudinal with the fixed structure of the combustion appliance.

  According to another preferred embodiment, the structure of the cylindrical register consists of a thin sheet, in particular of the order of 1 to 3 millimeters, for example rolled and welded to form a cylindrical shell of circular section, which is provided one or more annular or circumferential reinforcements (or stiffeners), which stiffen the structure of the register, which makes it possible to obtain a light register of simple construction; this reinforcement can be obtained (or constituted) by a fold or a circumferential undulation produced in the sheet of the

  register; alternatively, this structure is actuated manually.

  The presence of the sealing and reinforcement means has considerable advantages compared to the structure described in the patent.

FR 2,188,780.

  The cylindrical structure of these registers also ensures

  a very large passage section, and therefore a low pressure drop.

  This particular structure of multiple sliding dampers is particularly suitable for installations for the heating of outlet gases

  of gas engines or turbines, in cogeneration plants.

  In this type of installation, the gases escaping from the engine or the turbine are heated by causing them to burn; when the engine or turbine is in operation, these oxidizing gases are delivered in large quantities to the burners at a temperature of the order of 500 C; when the engine or the turbine stops, the burner is supplied with cold air, in a much smaller quantity; the system according to the invention makes it possible in this operating mode, by sealing one of the registers, to adapt to these variations in operating mode. This device is also suitable for air stage burners in which a first part of the combustion air is injected at the center of the burner, and the other part is injected by nozzles or by an annular space coaxial with the burner, on a diameter of the order of 1.2 to

  2 times the diameter of the internal circuit; these burners are intended to reduce emissions of nitrogen oxides.

  According to a preferred embodiment, the support, guiding and driving means in movement of each of the sliding cylindrical registers, are constituted by an articulated structure, preferably comprising at least two (in particular three) Watt parallelograms, as described in patent FR 2,188,780 the articulated structure is preferably actuated by a jack associated with each register, and extends outside and around the cylindrical wall

or ferrule of each register.

  As described in said patent, the deformable parallelogram structure linked to the cylindrical register by articulations (or pivots), is particularly suitable for supporting the register exposed to dust and soot, allowing displacement of the register without contact or friction against the structure fixture; as described in this document, the system essentially consists of: - two forks substantially in the form of a half-arc arranged around said register and each articulated around two pivots swiveling on fixed axes; - two articulated links connecting the two ends of the forks located on the same side of the register; - two diametrically opposite pivots, supporting said register and placed in the middle of said links; means for pivoting the two forks simultaneously around their pivots and at least one register guide device formed by two arms articulated around fixed pivots, the ends of the two arms being connected together by an articulated connecting rod carrying, in

  its middle, a pivot fixed to the outside of said register.

  The advantages of 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,

  unless otherwise indicated, the same references from one figure to another.

  Figure 1 illustrates in partial cross-sectional view a combustion device equipped with a burner associated with two oxidant transport channels, each equipped with a cylindrical sliding damper. Figure 2 is a simplified perspective view of the

register of figure 1.

  FIG. 3 illustrates in simplified cross-sectional (and longitudinal) view the application of the invention to a burner associated with means

  of combustion smoke recirculation.

  With reference to Figures 1 and 2 in particular, the combustion device 1 allows the production of a flame 2 in a

  combustion 3 delimited by walls 4 of refractory material.

  An orifice 5, for example cylindrical, extending along the axis 7 of general symmetry of the burner and of the combustion appliance, is provided.

  in the wall 4, inside which the burner 6 extends.

  This burner is associated with a duct 8, extending along the longitudinal axis 7 of symmetry, transporting a fuel (liquid or pulverulent) to the nose of the burner, as well as if necessary ducts 9 delivering gas (such as natural gas or LPG by

example).

  The wall 4 has a second annular orifice 10 which delimits a conduit 11 for transporting oxidant gas through the

wall 4.

  A fixed structure consisting of a cylindrical shell 13 of axis 7 and a flange 14 essentially, delimits a central duct 12 serving

  also to the delivery of oxidizer to the nose 6a of the burner 6.

  The apparatus 1 comprises a chamber 15 separated from the chamber 3 by the wall 4, and into which the conduits 8, 9 extend and a part of the structure 14, 13 of the burner, into which chamber 15 are admitted gases ( or the air serving as oxidizer) which are delivered by a duct

  16, according to a radial flow represented by arrow 17.

  The apparatus shown in FIGS. 1 to 3 comprises an internal cylindrical sliding damper 21, which is shown in the maximum open position in FIG. 1 and in an intermediate position in FIG. 3, and an external cylindrical sliding damper 19 represented in the position of closure in Figures 1 and 3; thus, the register 21 allows the passage along the arrow 20 of the oxidizing gases in the central channel 12 for transporting oxidant to the nose of the burner, while the register 19 prohibits the circulation 18 of oxidant to the second duct or channel transport of the oxidizer to chamber 3 of

  combustion, in the position shown in Figures 1 and 3.

  The register 21 mounted sliding along the axis 7, like the register 19, is substantially in the form of a cylindrical shell of circular section, the end 21a of which can come by sliding, in order to close the passage 33, in contact with a wall 23 delimiting the chamber 15 and through which the pipes 8 and 9 extend, as well as connecting rods 24 for driving the registers 19 and 21 in movement. The register 19 consists of a rolled sheet forming a ferrule cylindrical, provided (FIG. 1) in the central part with a corrugation 19b to reinforce it, extending from a first end 19a in contact with a flange 22 fitted to the wall 4 (in the closed position shown in FIG. 1), up to at a second end (19d in figure 2) or it is provided with a transverse flat sheet 19c (figures 1 and 3) forming a flange or crown and coming to bear against the flange 14 (forming part of the fixed burner support structure and from the

  combustion) to ensure a tight seal in this position.

  Each of the registers 19 and 21 is respectively supported, guided and set in motion by means of connecting rods 27 and 29 (with regard to the register 19), which connecting rods 27 and 29 (in the form of a fork) are linked by a joint. 27a, 29a to a central link 28 to which the damper 19 is fixed by a central articulation 28a, to form a Watt parallelogram, as described in the aforementioned patent; two Watt parallelograms arranged symmetrically with respect to a median longitudinal plane, as illustrated in FIG. 2 in particular, as well as a third Watt parallelogram 28, 34 serving as anti-rotation stabilizer,

  form the register guide system 19.

  Each of the forks 27, 29 in a semi-circular arc is articulated, by virtue of two pivots (arranged symmetrically on either side of a longitudinal plane containing the axis 7 and the axis of the control rod 24) 27b ( respectively 29b), with respect to bars or support rods

  , partially shown, which are linked to the fixed structure.

  The shell of the register 19 is thus suspended from the three pivots or articulations 28a of the three links 28; according to an alternative, the third link 28 of the third parallelogram 34, 28 can be replaced by a guide preventing rotation of the ferrule 19. An identical system or of smaller dimensions, comprising connecting rods or forks 30 and 32 and a central link 31 , allows in the same way the support, guiding and driving movement of the register 21; the registers are respectively actuated by two cylinders 25 and 26, by means of a rod or connecting rod 24 extending through the partition 23, and provided with an articulated connection with the fork

27 (respectively 30) ordered.

  With reference to FIG. 3, a similar device with a double sliding register is used in a combustion appliance equipped with means

  smoke recycling, and a mixed burner.

  Such a burner comprises a central duct 12 for supplying primary air, means 8 for injecting liquid fuel into the hearth 3 arranged inside the central duct 12 (in the axis of the latter), a stabilizer for flame 55 disposed coaxially inside this central duct 12, and several orifices 63 for supplying secondary air situated outside the means 8 for injecting liquid fuel and the duct 12; injection means 9 for gaseous fuel are arranged in a ring between the injection means 8 for liquid fuel and the orifices 13 o10 for supplying secondary air; these can be replaced by a single annular passage 11 arranged in a ring outside said

injection means 9 and 8.

  The apparatus comprises a ring 53, made of refractory material comprising all of the air supply, fuel injection and smoke recirculation orifices, which is mounted through the refractory wall 4 of the hearth 3 so that its front face 53, through which said orifices open, or projecting relative to the latter. The orifices 63 are placed peripherally in staggered rows between the orifices 74 for sucking the fumes in the hearth 3; these suction orifices 74 can be replaced by a single annular peripheral passage, but the presence of multiple orifices staggered makes it possible to avoid re-aspirating the secondary air in said smoke suction orifices and allows (conversely) 'prevent this secondary air supply preventing said fumes from being sucked (according to arrow 61) to be recirculated in the burner head; these two fluids exchange their calories inside the burner, thanks to a common wall 601 separating: - on the one hand a box 60 for distributing said recirculated fumes, supplied on one side by the suction orifices 74 of the fumes in the hearth 3, and reinjecting them after cooling, in conduits 59 for reinjection into the hearth, through which also open the injection means 9 of the gaseous fuel, l1 - on the other hand, a distribution box 64 of the secondary air, which on one side is supplied (arrow 18) by a supply duct 16, after passage through the register 19, and on the other hand (after this secondary air has been heated) injects it ci in the hearth by the channels 11 terminated by the orifices 63 defined above. The means 9 for injecting gaseous fuel and the means for reinjecting the fumes, which are preferably coaxial and have their orifices 9 combined, are located in a peripheral ring around the

flame stabilizer 55.

  To create a staging of the air intake relative to the flame of the liquid fuel, the injection ports of this fuel as well as those of the gaseous fuel and of the primary air supply, open out at the bottom of a bowl 56; the latter is disposed in hollow relative to the refractory wall 53 which surrounds it and through which open said orifices 63 and the fumes from the

  focus 2; the bowl may be in the form of a truncated cone.

  The injection means 9 for the gaseous fuel can be separate supply rods, arranged in a ring around the injection means 8 for the liquid fuel and located in the duct 12 for supplying primary air, or can be replaced by nozzles mounted on a single ring disposed peripherally in a ring around the injection means 8 of the liquid fuel, and supplied by

a single feeding rod.

  The means 8 for injecting the liquid fuel may include multiple orifices, creating several independent flames in the hearth 3 which may either be directed parallel to the axis 7 of the burner, or divergent and oriented towards the air supply orifices 63 secondary to improve the combustion of said liquid fuel after a first phase of

combustion with primary air.

  The sliding damper system according to the invention also advantageously applies to the burners described in application EP 774 620,

  which do not include smoke recirculation circuits.

Claims (10)

  1. A combustion apparatus (1) which comprises at least one burner (6) associated with two conduits (11, 12) for transporting gaseous oxidizer, characterized in that it comprises two cylindrical sliding registers (19, 21). 2. Apparatus according to claim 1, wherein said   registers are coaxial, mounted sliding along their common axis (7).   3. Apparatus according to any one of claims 1 or 2,   in which said registers are of different diameter, the ratio of the diameter of the external register to the diameter of the internal register being   less than or equal to 2 and greater than 1.   4. Apparatus according to any one of claims 1 to 3,   wherein at least one of the registers is provided with sealing means (19c). 5. Apparatus according to claim 4, wherein the sealing means comprise a thin crown fixed to one end longitudinal of the register.   6. Apparatus according to any one of claims 1 to 5,   in which the structure of the cylindrical register comprises a thin sheet   provided with one or more circumferential stiffeners (19b).   7. Apparatus according to any one of claims i to 6,   which comprises means for supporting, guiding and driving in translation each of the sliding cylindrical registers, which means essentially consist of an articulated structure actuated by a jack (25, 26) associated with a register, which articulated structure s '' extends outside and around the cylindrical or ferrule wall of each register.   8. The apparatus of claim 7, wherein said   articulated structure has three Watt parallelograms.   9. Apparatus according to any one of claims i to 8,   in which the combustion appliance comprises an oxidizer inlet duct (16) disposed upstream of the damper, which is not axial, in particular which is oriented radially with reference to the longitudinal axis   common oxidant conduits, dampers and burner. 10. Apparatus according to any one of claims 1 to 9, which comprises several burners, each equipped with several conduits   (19, 21) provided with sliding cylindrical registers, which burners are supplied with oxidant by a common conduit (16) radial or oblique.