CA1223775A - Burner for pulverized, gaseous and/or liquid fuels - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A burner for pulverized, gaseous and/or liquid fuels having an ignition chamber possessing a wall diverging rotationally symmetrically in diameter and an outlet pipe adjoining thereto, according to the present invention comprises an outlet, disposed centrally in the chamber wall, of a pipe for feeding a fuel jet and a twisting air inlet surrounding this outlet for feeding combustion air in twisting motion, which produces inside the ignition chamber a hot recirculation flow. This hot circulation flow thoroughly mixes the fuel jet and heats it to ignition temperature.
Only a portion of the total combustion air required can be introduced into the ignition chamber as twisting air via the twisting air inlet, and therefore in the region between the chamber wall and the outlet pipe a second air inlet is provided,through which a further combustion air portion, partially or entirely likewise mixing with the fuel jet, can be introduced into the ignition chamber. The sum of the combustion air portions participating inside the ignition chamber in the mixing with the fuel jet is adjusted to not more than 50% of the total combustion air required. The burner according to the invention is variable and flexible within very wide limits with respect to fuel type, calorific value of the fuel, and output rates. The flame of the burner is slender in form with small radial extraction. The burner will be useful for medium output requirements such as annealing and smelting furnaces, firing kilns for ceramic products and steam boilers.

Description

223~t~
K~rting Hannover AG 37~/28 Burner for pulverize , gaseous and/or liq~d fuels The continually steeply rising prices in recent years of liquid and gaseous fuels have provided a stimulus to increased use of solid fuels, which are frequently available at more favourable prices in a su~ficient quantity. The ~rate firing which is usual with solid fuels and is pre-dominantly used in the generation of steam and hot water is, however, not possible in many fields of industrial process heat, because as a rule specific requirements exist there in regard to the course and location of the combustion. For these fields, the solid fuels therefore can be used only as "dust" (i.e. in finely divided or pulverized Form), which can be burnt with appropriate burners in a flame similar to the flames of liquid and g~seous fuels.

;

The use. of pulverized fuels, predominantly pulverized coal, has hitherto been limited substantially to large furnaces with basically steady Firing conditions, especially Eor power stations and in the field of industrial process heat for the rotary kilns of the cement industry. There exists, however, an increasing demand for pulverized fuel firings for fields of application of medium output, for example in annealing and smeLting furnaces of the metal industry, firin~ kilns for ceramic products, smelting furnaces for hollow and sheet glass, steam boilers with combus-tion chambers or apparatuses for thermal treatment (such as, for example, driers with combustion chamber connected in front). These new fields of application require extraordinarily flexible burners, which, even under /highly

- 2 - ~2377S

highly varying lcad conditions, must give out a flame with a defined ignition and burn up behaviour (fl~me form). They must also be capable of processing pulverized fuels with varying ignitability and varying calorific value, since for reasons of price not onLy coal dust but also lignite dust, sawdust and dust from sewage sludge must be considered.
and also all other dusts provided they are sufficiently combustible.
From this arises the necessity of a specific burner technology, to which the concepts and experience from pulverized fuel large furnaces can be transferred to only limited extent. On the other hand, dust flames have a different ignitlon and burn-up mechanism from that of flames of liquid and gaseous fuels, so that recourse may also not be made to the hi~hly developed burner technology for liquid and gaseous fuels.

Normally, the pulverized fuel is supplied to a pulverized Euel burner in a mixture with a smsll quantity of conveying air as a comparatively compact jet. This jet must first be made ignitable, i.e it must be heated and thoroughly mixed with combustion air. In the preparation, a vapourizing off of the volatile constituents contained in the pulverized fuel material first takes place. As soon as a sufficiently high temperature is reached, these volatile constituents then ignite and burn, and therea~ter the burning up of the combustible solid constituents takes place. Such an ignition and burn-up mechanism depends firstly upon the particle size of the fuel dust (smaller particles are heated more rapidly) and secondly upon the pulverized fuel material itself, since the contents of volatile con-stituents, water and ash exhibit a considerable variation in the different materials.
/Large

- 3 ~ 3~

Large installations are normally operated with mainly constant pulverized fuels, so that larger fluctuations in type and quality of the pulverized`
fuel do not have to be taken into account. In general, in the burners intended for large installationsJ the fuel jet is introduced directly into the co~bustion 6pace . The preparation and ignition of the fuel jet takes place (either only in the thermal conditions in the combustion 9 p~C e or with assistance from oil or gas as supporting fuel) in that the hot gases present in the combustion spaco recirculate towards the outlet of the burner and penetrate into the fuel jet. Further additional measures may be provided, which-favour the penetration of the hot gases into the fuel jet and contribute to stabilizing of the ignition operation.
For example, the Euel jet can be fanned out to conical form to greater or lesser extent by twisting or blowin~ in oE air. A corresponding e~fect is obtained iE the combustion air is supplied around the burner outlet and is so influenced, by partial blocking or conical divergence of the air pipe outlet or by twisting, that a suction zone is created near to the root of the jet. With increasing fanning out of the fuel jet, however, the flame becomes shorter and more bulky and moreover dust particles and ash particles are increasingly loosened Erom the cohesion of the flame and carried radially outwards.

These burners which operate with preparation and ignition of the fuel jet in the combustion spDQe are not suitable for variable requirements, because the ignition operation can then no longer be kept stable, Further more, an ignition stability accompanied by more pronounced fanning out of the fuel jet cannot be permitted in many fields of industrial process heat, because the radial particle removal can lead to pollution of: the product and Igive 3~

give rise to problems in the combustion s~ace . Thus, in hot combus-tion chambers with temperatures above approximately 1100C, the extracted ash particles become soft or even liquid and lead to the forming of scale and corrosion phenomena. In less hot combustion space~ , the extracted ash particles do, indeed, remain sufficiently solid, but the extracted dust particles no longer ignite or become extinguished before complete burn-up, which in each case represents a loss of fuel. Long, slender flame forms with the least possible extraction of particles towards the outside are therefore desired.

It has also already been proposed not to ignite the fuel jet as late as the combustion space, but to igni~e it already in a special ignition chamber connected beEore the burner outlet. Such a type oE burner has been described by ~. Schoppe in the Brochure "Berechnung von Br~nnern, ~rennk~mmern und ahnlichen StrUmungsapparaten", ("Design of burners, combustion chambers and similar flow apparatuses"), Verlag A.W. Gentner KG, Stuttgart (no date stated) pages 37 et seq ~e ignition chamber here has a conically diverging wall, which has its transition into an outlet pipe leading into the combustion chamber. Centrally in the chamber wall, the mouth of a pipe for supplying the fuel jet is disposed, and this mouth is surrounded by an air inlet (e.g. an annular gap), through which the combustion air is introduced into the combustion chamber in the form of a twisting flow, in order to generate a suction zone near to the root of the jet.

In operation, the twisting flow flows along the ch~nber wall to the end of the chamber, where it divides into ~wo flow parts. The flow part near /to the ~J~

~2~3~

to the wall passes via the outlet pipe into the combustion space, whereas the remaining part, due to the suction zone, is conducted b~ck in a recirculation flow, that is in the opposite direction,along the fuel jet to the root of the jet. As a result, the hot gases, which are pro-duced by the combustion processes takin~ place in the ignition chamber, are conveyed to the root of the jet, so that even just after the outlet of the fuel pipe a preparation and ignition of the outer peripheral zone of the fuel jet commences, which (ignition) then propagates, because vortices ~orm between the fuel jet and the recirculation flow in the opposite direction, comparatively rapidly into the interior ofthe fuel jet.

This burner has been developed Eor Eairly small outputs (e.g. for central heating boilers) and has some basic disadvantages which render it un-suitable for operation at medium outputs and especially in the field of industrial process heat. Since, for various reasons, the entire com-bustion air must be introduced as a twisting flow into the ignition chamber, not only an ignition but also a considerable combustion of the pulverized fuel takes place in the ignition chamber, so that only a short flame consisting of almost burnt fuel dust leaves the mouth of the burner.
The fuel jet is almost completely broken up in the ignition chamber, with the result that ash particles are carried in considerable quantity to the chamber wall. If the burner output is not sufficiently small, such high temperatures occur in the ignition chamber that these ash particles become liquid or sticky and can lead to the forming of baked scale. Moreover, in each case, a portion of the twistine flow passes into the combustion /space - 6 - ~ ~ ~37~S

space and gives rise there to a radial extraction of further ash and pulverized fuel particles.

With the invention a burner i5 to be created, which exhibits a stable ignition also at medium output rates and variable requirements, and which provides in the combustion space a long, s~ender form of flame with small radial extraction.

Starting from the known burner with central feed of ~he fuel jet and of twiseed combustion air rnixing with the fuel jet into an ignition chamber, the invention achieves this objecti~e in that only a proportion of the total combustion air required can be introduced into the ignition chamber via the twisting air inlet, that in the region between the chamber wall and the outlet pipe a second air inlet is provided, through which a Eur~her propor~ion of comb~lstion air, entirely or partly likewise mixing with the fuel jet, can be introduced into the ignition chamber, and that the sum of the combustion air portions participating inside the ignition chamber in the mixing with the fuel jet is adjusted to not more than 50% of the total combustion air required.

The invention is based upon the purposeful utilization of the knowledge that a burner equipped with an ignition chamber must in principle be capable of being used for variable requirements even at medium outputs and especially in the field of industrial process heat, if success is achieved in overcoming the previous disadvantages of this type of burner, Surprisingly, it has been found tha~ these disadvantages can in actuality be completely eliminated by a favourable cooperation of a plurality of /measures, _ 7 _ ~2~37~5 measures, namely - to state it brieEly - by the fact that the ignition chamber is operated with substoichiometric combustion air and the intro-duction of the substoichiometric combustion air takes place in a specific manner through two inlets.

In operation of the burner, the portion of comb~istion air fed as twisting air via the first inlet into the ignition chamber forms around the fuel jet a suction zone, which leads to the result that the fuel jet is somewhat fanned out and that a~ the same time a hot recirculation flo~7 streams back to the root of the jet. This formation of a suction zone is assisted by the other portion of combustion air, which is supplied via the second inlet and surrounds in annular manner ~he fuel ~et, in such a way tha~ e~en a small quantity of twisting air is sufficient ~or the stable ignition oE the Euel jet. The further combustion air introduced via the second inlet has, however, also other functions.
Thus, it has the effect that the twisting flow has a better transition into the recirculation flow and can flow away less ~strongly with its portion near to the wall through the outlet pipe. It also ensures that this transition takes place within a defined and predeterminable cross-sectional zone of the ignition chamber, that is to say the axial length o the recirculation zone can be influenced according to needs~ Moreover, it entirely or at least largely breaks down, in the outlet pipe, the twisting fl~w of the twisting air and also a twist which is present in the fuel ~et (which can be produced by a special twist generator and/or by the action of the twisting air), so that the pulverized fuel particles are brought into a predominantly axial flow direction at latest at the /outlet - 8 ~ ~Z23775 outlet of the burner. For this purpose it may be in individual cases appropriate to provide the further combustion air with a COUnteT-twiSt.
In addition, the further combustion air cools the outlet pipe and prevents residues, especially molten ash particles, from precipitating in it.

For the invention it is also important to set substoichiometric com-bustion conditions in the ignition chamber. This again has a plurality of functions. Firstly, the fuel jet is only broken down to a limited extent inside the ignition chamber, and the radial extraction of particles inside the ignition chamber is correspondingly low. Furthermore, there is available to the fuel jet only a quantity of air which indeed is sufficient for igniting and commencement of combustion, but no longer sufficient for continuous combustion, which has the result that the burn-up of the fuel jet takes place predomlnantly in the combustion space and the ignition chamber~P~ains corresponding cooler.

In total, therefore, the cooperation of the measures of this invention provides a burner which is variable and flexible within very wide limits, and which can also be operated at medium output rates free Erom disturbing ash scale formation, and which delivers a fuel jet as free from twist as desired and completely i~nited with a largely axial flow direction, which jet has reached a temperature of approximately 700 - 1200 C at the burner outlet, depending upon the fuel used and the operating conditions required.
Thus, in every combustion space - whether hot or less hot - a stable burn-up of the fuel jet with long, slender flame form is assured.

The substoichiometric portion of the combustion air required in the ignition /chamber ~L~23~75 g chamber likewise depends upon the fuel used and upon the required operating conditions and results from that quantity of the ~otal c~m bustion air introduced into the ignition chamber, which mixes thoroughly with the fuel jet and thereby participates in the ignition and commence-ment of combustion. The combuction air introduced into the ignition chamber is composed of the propelling air for the pulverized fuel (con stituting approximately 2 - 7~ of the t~al air)~of the twisting air supplied through the first inlet (constituting approximately 2 -15% of the total air) and of the further combustion air supplied through the second inlet. 0f these, the propelling air completely participates and the twisting air almost completely participates in the mixing with the fuel jet, whereas the Eurther combustion air may be treated in various ways. It can be of such quantity and so conducted that it is completely mixed, in which case its quantity results from the requirement that the sum of the mixed combustion air must not amount to more than 50% of the total air. On the other hand, the quantity of this further combustion air may also be of greater magnitude and may if required even constitute the complete remainder of the total air, provided, for example, that assurance is provided by appropriate flow guidance that only the maximum permitted part mixes with the fuel jet, whereas the remaining portion emerges into the combustion space unmixed around the fuel jet, With this different handling of the further combustion air, a possibility is provided of influencing the flow and temperature profile at the burner outlet.

An advantage of the invention is moreover also that the burner is not restricted to the use of pulverized fuels, but can be operated directly /in the ,~

- 10 - ~ ~37~5 in the same manner wîth liquid or gaseous fuels. With pulverized fuel as the principal fuel and gas or oil as suppor~ing Euel, it is sufficient, for example, ~o shut off the main fuel and to run up the supporting fuel to full output without interrupting operation of the burner9 if this should be necessary in the case of bottlenecks in the supply of pulverized fuel. It is also possible for gas andtor oil, especially heavy oil which is difficult to ignite, to be provided as principal fuel.

Numerous embodiments and further developments of the burner of this invention are defined in the sub-claims and are explained in more detail in the Eollowing description of individual forms oE embodiment with reference to the drawings. In these, like or functionally like components are given the same reEerences. The drawings show:

ig. 1 in longitudinal section, a burner for pulverized fuel as principal fuel and with gas as supporting fuel Fig. 2 a cross-section through the burner in the plane II-II
of fig. l;
Fig. 3 in longitudinal section, a burner with a different form of the inlet Eor introducing the Eurther combustion air into the ignition chamber Fig. 4 in longitudinal section, a burner with a different form of inlet for introducing twisting air into the ignition chamber;
Fig. 5 in longitudinal section, a form of the burner modified from that of fig. 4;
IFig. 6 2~37~5 Fig. 6 a cross-section through the burner in the plane V-V
of fig. 5 Fig. 7 in longitudinal section, a further form of embodimen~
oE a burner for pulverized fuel as pri~ncipal fuel, with gas as supporting fuel Fig. 8 a cross-section through the burner in the plane VIII-VIII of fig. 7;
Fig. 9 in longitudinal section, a burner for pulverized fuel with a modified feed for the support gasi Fig. 10 in longitudinal sec~ion, an ignition chamber with a form of the inlet modified from that oE fig. 1 for ~e Eurther combustion air~
Fig. 11 in longitudinal section, a burner for pulverized fuel as principal fuel and oil as supporting Euelt Fig. 12 a cross-section through the burner in the plane XII-XII of fig. 11;
Fig.13 in longitudinal section, a burner for liquid fuel with twist atomization;
Fig. 14 in longitudinal section, a variant of the burner according to fig. 13 and Fig. 15 in longitudinal section, a variant of the burner according to fig. 14 i ' 37~

The form of embodiment illustrated in Fig~ 1 and 2 illustrates the principle of the burner of this invention by the example of pulver-ized fuel as principal fuel in conjunction with gas as supporting fuel~ Inside an air pipe 16, three concentric pipes 1, 2 and 3 are provided, which lead jointly into an i~nition chamber 20. Of these three pipes, the central pipe 1 serves for feeding the fuel jet, the middle pipe 2 for feeding the supporting gas and the outer pipe 3, equipped at its outlet with a twist generator 21, for feeding twisting air into the chamber 20. In the embodiment illustrated, this twist generator consists of an insert closing the pipe 3~ in which insert a twist annular chamber 4 is situated~
which is in co~munlcatio~l via tangential bores 5 with the internal space of the pipe 3 and via an inlet 50 with the chamber 20.
Advantageously, a restricting threshold 22 is disposed at the inlet 50, which prevents backflow out of the chamber 20 into the twist annular space 4.

The chamber 20 is bounded by a domed wall 8, which extends outwards from the twisting air inlet 50, and by an outlet pipe 17, disposed downstream therefrom, which may be of cylindrical form, but which likewise may also increase or decrease in diameter. In Fig. 1 full lines show that the outlet pipe 17 is reduced to the diameter of a cylindrical outle~ component 11, while at the same time a cylindrical construction of this outlet pipe is indicated in broken line at 17'. Between the wall 8 and the outlet pipe 17, the chamber 20 possesse6 a second annular inlet 60, which is formed by the outlet pipe 17 having at this position a somewhat larger diameter than the wall 80 The aperture cross-section of this /inlet ~- 13 - ~2~3~
inlet may advantageously be adjustable For this purpose, for example, the outlet pipe 17 may be displaceable in the axial direction of the air pipe 16, or a thrott;le element, not shown in Fig. 1, displaceable in the axial direction of the air pipe 16, may be provided externPlly on the chamber wall 8.

In operation of the burner according to Fig. 1 and 2, the support-ing gas together with the twisting air is first supplied into the chamber 20 and caused to combust. Thereafter the pulverized fuel jet consisting of a pulverized fuel-propelling air mixture is fed to the chamber 20. In the pipe 1~ a twist generator 2~ may ~urther be providod, in order to fan out the fuel ~et in the chamber 20 into conical ~orm~ as indicated by the arrow~ h. The twisting air issuing from the inlet 50 ~lows along the chamber wall 8 outwardly and then, as indicated by the arrows B, changes into an internal recirculation. Consequently, the hot ga6es which result ~rom the combustion processes taking place in the chamber 20 are transported to the root of the fuel jet, so that a stable ignition oY the fuel jet takes place and the jet is com-pletely ignited right through at the burner outlet 49, The principal proportion of the total combustion air required is, in the embodiment according to Fig. 1 and 2, supplied through the air pipe 16 and flows partly externally past the chamber 20 directly into the combustion space as indicated by the arrows D, but also arri~-es partly via the i~let 60 into the chamber 20 and flows there according to the arrows C along the outlet pipe 17 to the burner outlet 49. This partial air stream C, entering the /chamber - 14 ~ 3 ~ ~

chamber 20, can make up approximately 5-45% of the total air and constitutes the further combustion air portion, which is at least partly brought into ignition and commencing combustio~ of the fuel inside the chamber 20, in addition to the twisting air and the propelling airO Thus, the combustion air available in the combustion space for the complete burn-up of the fuel jet is obtained from the outer partial stream D and possibly also an unburnt residue of the partial air stream C.

If the partial air stream C is to be furnished with a counter-twist to promote its twist-reducing effect, the most simple way of achieving this i8 to dispose~ in the region of the inlet 60, correspo~ding twist generator~, whiah are not lllustrated in ~g. 1.

In addition, it ie advantageous to supply the twisting air to the burner with a pre-pressure raised above that of the principal air, in order that even with a small quantity of air adequate twist energy can be produced. ~he typical range for the pre~
pressure of the combustion air in the main pipe 16 lies between approximately 0.01 and o.o6 bar gauge, whereas the pre-pressure of the twisting air in the pipe 2 can be approximately o.o8 to 0.4 bar gauge.

Fig. 3 shows a burner in which the introduction of the partial air stream C into the chamber 20 is provided through a pipe 10, which is disposed concentricaLy to the central pipe 1 and is connected via a number of inclined bores 29 with the chamber 20. In this form of embodiment~ the chamber wall 8 is flat and the outlet pipe - 15 ~ ~23~

61 adjoining the bores 29 is of cylindrical form, which however in no way modifies the basic method of functioning of the burner. A180, as in F~g. 1, the twlst-cancelling effect of the partial air stream C can be still further promoted by the fact that, in the pipe 10~ means for generating a counter-twist are provided or the bores 29 are di~posed correspondingly incli~ed also in the tangen-tial direction. The feed of the partial air stream D into the combustion space can take place in a manner a~alogous to Fig. 1 via an air pipe 16, but is favourably effected via separate air inlets, in front of each of which air preheater~ may be connected.
Neither of these is further illustrated.

In the form of embodiment according to ~ig. 3 it is possible to in~luonce tho length of the recirculation range of the twi~3tin~
air during burner operation by appropriate ad~usting of the quantity and possibly of the ~low velocity of the partial air stream C, so that the recirculation range either extends as far as the outlet 49 (arrow~ B') or is forced back to the bores 29 (arrows B).
Consequently it is possible to aohieve the effect that the twisting stream is never cancelled out until it has fulfilled its function, which is important, for in~tance, when uRing pulverized ~uels with Yarying properties. If required, the partial air stream C may also be so ad~usted that it makes up the entire quantity of the combustion air required, and there~ore no residual combustion air needs to be introduced separately into the combustion space.

The form of embodiment according to Fig. 4 corresponds largely to that of Fig~ 3, but provides the introduction of two twisting air /streams ".

- 16 ~ 7 ~ ~

ætreams into the chambe~r 20. The wall of the chamber 20 is here subdivided into an inner wall part 8 and an outer wall part 9. The first twisting air stream is supplied, analogously to Fig. 1, via a pipe 27 and the bore 5 to the twisting annular space 4, so that it enters the chamber 20 in twisting motion from the inlet 50.
For the second twisting air stream, an additional annular i~let is provided between the wall parts o and 9, which is supplied through a pipe 28 concentrically surrounding the pipe 27 and a second twisting annular ~pace 7 connected therewith via tangential bores 6. The partial air stream C i9 again supplied through the pipe 10 and is introduced via an annular inlet 60 into the chamber 20~ the outlet pipe 62 of whiah is slightly conically dlverging.
In this form of embodiment~ the additional advantage iB obtained that the twisting floW9 due to the greater diRtance between the additional ~nnular inlet 51 and the chamber axis, possesses a higher rotational impulse.

In the embodiment according to Fig. 5 and 6, as in Fig. 4, the wall of the chamber 20 is subdivided into the inner wall part 8 and the outer wall part 9. The total twisting air is, however, supplied through the pipe 3 and introduced via the bores 5 and 6 both into the inner twisting annular space 4 and also into the outer twisting annular space 7.

/From ~rom the twist annular spaces 4 and 7~ the twist air then flows through the inlets 50 and 51 onto the wall parts 8 and 9, conically shaped in this case. The outlet pipe 17 of the chamber is mounted on the outer pipe 10~ through which the partial air flow C is conducted externally past the wal.l component 8 into the chamber 20. In addition, in Fig~ 5, twist generating means 18 are also illustrated in the pipe 10.

Ln the forms of embodiment according to Fig. 1 to 6, the twist of the twisting air issuing from the inlets 50 and 51 is pro-duced by bores 5 and 6, which are introduced tangentially into the twist annular spaces 4 and 7. Instead, however, guide blade gratin~ can be u~ed for gener~tin~ the twi3t~ as illustrated in Fig. 5 at 18. Such an arrangement is shown in Fig. 7 and 8.
The inlets 50 and 51 each have their own pipes 14 and 15 associated with them, in which guide blade gratings 12, 13 res-pectively for generating twist are disposed. In addition, to eliminate the twist, guide edges 23 are provided in the outlet portion 11 of the outlet pipe. Moreover, desired turbulences may also be produced by a radial barrier surface 19, disposed externally on the outlet part 11~ on the pa.th of the combustion air flowing externally past the chamber 20.

Fig. 9 shows a variant of the forms of embodi~ent so far described of the burner of this invention, such that the supportin~ ~uel is introduced into the chamber 20 through an internal pipe 25 disposed in the fuel pipe 26. mus the fuel feed takes place through the annular gpace which is formed between the pipes 25 and 26.
/In .~ .

;2%;37~5 In the form of embodiment according to Fig. 10, a varied form of th~ inlet for the partial air stream C is illu~;trated. The chamber wall 9 is connected, in the region of its maximum dia-meter, with the outlet pipe 17, the inlet for 1;he partial air stream C being formed by bores 29 or slits 58.

/In 37~7S

In the form of Pmbodiment according to Fig. 11 and 129 by contrast to the preceding examples, oil is u~ed as the support-ine fuel. The feed of this supporting oil :is effected via a pipe 30 coaxially surrounding the central ~uel pipe 1, which 5pipe 30~ is closed at its end and is connected via radial bores 31 with a further coaxial pipe 33, into which atomizing air is introduced. The supporting oil then issues, togethex with the atomizing air, from the outlet }2 of a duct 54 into the chamber 20. The bores 31 can, if desired, be arran~ed obliquely, in order to impart a twi~t to the supportlng oil.

It i8 A180 possible~ however~ to use oil (espeoially h~avy oil) a~ principal ~ue}. Form~ of embodlmont sultable for thi~ are shown in Fig. 13 - 15. A common feature of these embodiments is that only the fuel supply needs to be adapted to the use of oil, whereas the form of the ignition chamber and its operation with twisting air and with the further combustion air (partial air stream C) remains unchanged.

In the ~or~ of embodiment according to Fig. 13, a twist atomizin~
o~ the principal oil with additional twisting oil is provided.
The principal oil is introduced into the chamber 20 through a central pipe 35 ~ia a twist device 40, an outlet nozz}e 41 adjoinillg the pipe 35. Through a pipe 36 surrounding the central pipe 35, oil is also supplied~ which oil is introduced via bores 37 tangentially into a twist chamber 38, passes thence into a fuel nozzle 39 disposed in front of the outlet zone of the outlet nozzle 41, and emerges from this nozzle together with the principal oil into the chamber 20. lhe outlet nozzle 41 is preferably /mounted _ 20 _ ~ ~2377~

mounted axially displaceable relative to the fuel nozzle 39. Further-more, the pipe 36 i8 advantageously ~urrounded by a pipe 42 $or supplying the twisting oil, which forms an annu:Lar jacket closed at its end, into which a heating medium can be ~ntroduced for pxeheating the fuel.

In the burner illustrated in Fig. 14~ of which only the inner part is shown, a twist atomizing o~ the principal oil with twist oil alBO takes place. The principal oil is, in this case, introduced through a central pipe 45, which i8 furnished at the forward end with an outlet nozzle 53, in front of the outlet 46 of which the fuel nozzle 39 is situated. Together with the principal oil iss~ing ~rom the outlet 46, twisting oil enters the fuel nozzle.
The twisting oil is suppliedt as in Fi~. 13, through the pipe 36, is subjected to a twist by mean~ of the bores 37, and entsrs the nozzle 39 via the twist chamber 38. In this form of embodiment, the position of the pipe 45 relative to the fuel nozzle 39 cannot be changed. Instead, a central nozzle needle 55 is disposed axially displaceable in the pipe 35, by the conical tip 59 of which needle the issuin~ quantity of oil can be ad~usted. Moreover, the principal oil may also be introduced with twist into the fuel nozzle 399 by disposing a twist device 48 in the space between the nozzle needle 55 and the pipe 450 The burner illustrated in Fig. 15 differs in construction from the burner according to Fig. 14 only in that, instead of the central nozzle needle 55, a central pipe 4~ i6 present9 which is mounted axially displaceable in the pipe 45. The forward snd 47 of this _ /pipe ~3~S
r 21 ~

pipe 43 is conically shaped for adjusting the fuel feed through the nozzle 53 and also contains a passage 44, through which ~ir can be blown into the fuel nozzle 39, in order to promote the atomizing of the principal oil by the twist oil. Here again, as in Fig. 14~ a heating jacket can be provided, which however is not shown here.

/CLAIMS

Claims (20)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Burner for pulverized, gaseous and/or liquid fuels, contain-ing an ignition chamber possessing a wall diverging rotationally symmetrically in diameter and an outlet pipe adjoining thereto, and comprising an outlet, disposed centrally in the chamber wall, of a pipe for feeding a fuel jet and a twisting air inlet surrounding this outlet for feeding combustion air in twisting motion, which produces inside the ignition chamber a hot recirculation flow, which thoroughly mixes the fuel jet and heats it to ignition temperature, characterized in that, only a portion of the total combustion air required can be introduced into the ignition chamber (20) as twisting air (B) via the twisting air inlet (50,51), that in the region between the chamber wall (8,9) and the outlet pipe (17, 11, 17', 61, 62) a second air inlet (60, 29, 58) is provided, through which a further combustion air portion (C), partially or entirely likewise mixing with the fuel jet (A), can be introduced into the ignition chamber, and that the sum of the com-bustion air portions participating inside the ignition chamber in the mixing with the fuel jet is adjusted to not more than 50% of the total combustion air required.

2. Burner according to Claim 1, characterized in that the second air inlet (60, 29, 58) for the further combustion air portion is so arranged inside an air pipe (16) for feeding combustion air that a portion (C) of this combustion air enters the ignition chamber (20) and the remaining /portion portion (D) flows past the ignition chamber into the combustion space.

3. Burner according to Claim 1, characterized in that the second air inlet (60,29,58) for the further combustion air portion (C) is connected with a separate feed pipe (10).

4. Burner according to Claims 2 or 3, characterized in that the second air inlet (60) is formed as an annular gap between the chamber wall (8,9) and the outlet pipe (17, 17').

5. Burner according to Claims 2 or 3, characterized in that the second air inlet consists of a number of bores (29) or openings (58), which are disposed in the region of the transition from the chamber wall into the outlet pipe.

6. Burner according to Claim 2 or 3, characterized in that a twist generator (e.g. 18) for generating a twist oriented in the opposite direction to the twist air (B) is associated with the second air inlet (60,29,58).

7. Burner according to Claim 2 or 3, characterized in that the aperture cross-section of the second air inlet (60,29,58) is arranged adjustable.

8. Burner according to Claim 1, characterized in that the wall (8) of the chamber (20) adjoins in conically or domed diverging form the twisting air inlet and the latter is connected with a separate air-feed pipe (3,27,14) containing, in its outlet zone, a twist generator (21,13).

9. Burner according to Claim 8, characterized in that the wall of the chamber (20) is subdivided into an inner wall part (8) and an outer wall part (9), the inner wall part adjoins the twisting air inlet (50) and that, between the two wall parts, an additional twisting air inlet (51) is disposed, wherein a partial stream of the total twisting air provided can be introduced into the chamber through each of the two inlets.

10. Burner according to Claim 9, characterized in that each of the two twisting air inlets (50,51) is connected with a separate air feed pipe (27,28), each possessing, in its outlet zone, a twist generator (4,5,6,7,13).

11. Burner according to Claim 9, characterized in that both the twisting air inlets (50,51) are connected with a common air feed pipe (3), which possesses two twist generators (4,5,6,7) associated with the two inlets.

12. Burner according to one of Claims 8 to 10, characterized in that the air intended to twisting can be introduced into at least one of the air feed pipes (3,27,28,14) with a pre-pressure raised above that of the other combustion air portion (C).

13. Burner according to one of Claims 8 to 10, characterized in that one or both of the twisting air inlets (50,51) is formed as an annular gap.

14. Burner according to Claim 1, with a pulverized fuel as principal fuel, characterized in that, inside the first twisting air inlet (50), the outlets of a central pipe (1) and of a pipe (2) surrounding this concentrically are disposed, one of the pipe outlets serving for supplying the principal fuel and the other serving for supplying a twisted or non-twisted support gas.

15. Burner according to Claim 1 with pulverized fuel as principal fuel, characterized in that, inside the first twisting air inlet (50), the outlet of a central pipe (1) for supplying the principal fuel and the common outlet (32) of a pair of pipes (30,33) concentrically surrounding the central pipe for supplying supporting oil charged in twisting or non-twisting manner with atomizing air, are disposed.

16. Burner according to Claim 1 with oil as principal fuel, characterized in that, inside the first twisting air inlet (50), the outlets of a central pipe (35,45) having an outlet nozzle (41) for the principal fuel and of a pipe (36), surrounding this concentrically and equipped with twist generating means (37), for supplying liquid twisting fuel, are disposed, a fuel nozzle (39) being disposed in the direction of flow after the outlet nozzle (41), through which the principle fuel and the twisting fuel flow jointly.

17. Burner according to Claim 16, characterized in that the outlet nozzle (41) and the fuel nozzle (39) are mounted displaceable relative to each other.

18. Burner according to Claim 16, characterized in that, in the central pipe (45), a nozzle needle (55) adjustable in the axial direction is diposed.

19. Burner according to Claim 18, characterized in that the nozzle needle is formed as a pipe (43) adjustable in the axial direction, through which atomizing air can be introduced into the fuel nozzle (39).

20. Burner according to one of Claims 16 to 18, characterized in that the pipe (36) for supplying liquid twisting fuel is surrounded by a heating jacket (42).