CA2026857A1 - Process for exploiting a burner and burners for a rotary tubular furnace - Google Patents
Process for exploiting a burner and burners for a rotary tubular furnaceInfo
- Publication number
- CA2026857A1 CA2026857A1 CA002026857A CA2026857A CA2026857A1 CA 2026857 A1 CA2026857 A1 CA 2026857A1 CA 002026857 A CA002026857 A CA 002026857A CA 2026857 A CA2026857 A CA 2026857A CA 2026857 A1 CA2026857 A1 CA 2026857A1
- Authority
- CA
- Canada
- Prior art keywords
- burner
- air
- axial
- annular
- primary
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D17/00—Burners for combustion conjointly or alternatively of gaseous or liquid or pulverulent fuel
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C7/00—Combustion apparatus characterised by arrangements for air supply
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to a process for exploita-tion of a burner and to a burner for rotary tubular furnaces, wherein fuels and primary combustion air are supplied concentrically and the burner comprises a burner nozzle which comprises concentric supply conduits for the fuel and for the primary combustion air in the form of axial air and eddying air. In order to procure a process and burner which may operate with a smaller proportion of primary air and a greater range of adjustment, a dead zone is provided at the centre of the flame directly all around a central fuel conduit and within an annular fuel supply conduit, in which a very small proportion of fuel is sent.
This invention relates to a process for exploita-tion of a burner and to a burner for rotary tubular furnaces, wherein fuels and primary combustion air are supplied concentrically and the burner comprises a burner nozzle which comprises concentric supply conduits for the fuel and for the primary combustion air in the form of axial air and eddying air. In order to procure a process and burner which may operate with a smaller proportion of primary air and a greater range of adjustment, a dead zone is provided at the centre of the flame directly all around a central fuel conduit and within an annular fuel supply conduit, in which a very small proportion of fuel is sent.
Description
2 ~ 7 FIELD OF THE INVENTION
The present invention relates to a process for exploitation of a burner for a rotary tube furnace, in which fuels and primary air are supplied concentri-cally.
The present invention also relates to a burnerfor a rotary tube furnace equipped with a burner nozzle fitted with fuel and primary air conduits whlch are disposed substantially concentrically with 10 respect to one another, which primary air includes air set in rotation and air flowing axially.
BACKGROUND OF THE INVENTION
A burner of this type is disclosed in German Patent DE 2 905 746.
This known burner comprises, in addition to a central fuel admission for the oil, another fuel admission disposed concentrically thereto for powdered coal or any other like fuel.
For the purpose of obtaining a good mixture, 20 this solid fuel admission lies between two streams of primary air, of which one, which is the central stream, is set in rotation or eddy, i.e. it comprises a component in tangential or peripheral direction, and of which the other, outer, stream comprises an essentially axial flow velocity for the purpose of stabilizing the flame which penetrates far in the rotary furnace.
In other known burners, the stream of primary air is also provided to extend relatively far in the interior.
The known burner comprises, at its centre, a liquid fuel, generally oil, admission. The liquid fuel is atomized into fine droplets by means of a spray nozzle and is mixed, after leaving the central opening of the nozzle, with primary air which issues from the opening for outlet of eddying air, which opening is located radially around the central opening.
The known burners are usually employed with a proportion of primary air of between 8~ and 25%
of the total quantity of combustion air.
The power of the burner, i.e. the operational working, is regulated by a respective reduction or increase of the fuel and the air admission within a determined range of adjustment, in which the minimum adjustable working for obtaining a stable flame is equal to about 20 to 25~ of the maximum working pos-sible.
When the burner is started, oil must, as a general rule, be injected through the central orifice of the nozzle and must be ignited in order to pre-heat the furnace, since combustion of the solid fuel, which is supplied concentrically, is possible only in a sufficiently pre-heated furnace.
With respect to this state of the art, the present invention has for its object to provide a process for exploiting a burner of a rotary tube furnace and also a burner adapted to carry out this process, which may operate with a smaller proportion of primary air and present a broader range of adjustment of the operational working.
SUMMARY OF THE INVENTION
As far as the process is concerned, this object is attained by providing directly all around a central fuel supply conduit and/or radially inside an annular fuel supply conduit, a central dead zone in which, at the most, a reduced proportion of the primary combustion air is sent.
Thanks to the presence of a central dead zone, combustion thus begins at a greater distance in front of the centre of the nozzle of the burner compared 2~2~
3_ with the heretofore known processes and burners.
In this way, seen in longitudinal section, star-ting from the centre of the front end of the nozzle, the resultant f]ame comprises a central zone which S extends forwardly and radially, in which virtually no noteworthy combustion of the fuel is produced with the oxygen of the air.
It is true that such a central flame heart is also present in principle in the known burners, whilst, according to the present invention, this central dead zone is provoked deliberately and enlarged, more particularly by the fact that the least primary air possible is supplied in this zone.
However, even if it is not provided in the first place for combustion, a small proportion of primary air may be supplied in this central zone, this small proportion of primary air serving, however, in the first place to stabilize the flame and to prevent a rearward return of the combustion gases, the coal ash and the coke, which, without that, would lead to the soiling of the central part of the nozzle.
A small stream of primary air in this central zone, which is below 20% and preferably below 10%
of the total primary air, avoids such a rearward return of the combustion products, without supplying much oxygen which would reduce the central zone rich in fuel.
It has been unexpectedly found that, thanks to the presence of such enlarged central dead zone, the range of adjustment of the burner may be conside-rably increased, up to less than 10% of the maximum working for which the burner is designed.
Insofar as such a burner must operate especially with solid and pulverized fuels, this means that, after a brief pre-heating with oil, it may already 2~3~7 function with the solid fuel.
At the same time, it has been shown that, in such a process and in a burner designed for this process, the proportion of primary air which must be used for stabilizing the flame may be reduced by 2 to 10% and preferably below 6% with respect to the overall quantity of combustion air. This facili-tates manufacture of the primary air supply devices which may be designed respectively weaker.
A particular advantage of the reduced consumption of primary air resides in the resulting saving of energy for an equal performance and also in the reduc-tion of the proportion of nitrogen oxides in the combustion gases.
According to the invention, it is provided that, separately from the introduction of a small proportion of primary air in the central zone, at least two other separate streams of primary air are supplied, one of which is essentially axial and the other has 20 a major part of the flow components in peripheral direction.
As far as the device mentioned above is concerned, the object of the invention is attained by locating the orifices for admission of the eddying air and 25 of the axial air, outside the orifices for admission of the fuel, and the minimum radial distance with respect to the centre of the nozzle of the burner - from the outlet orifices for the eddying air and the axial air, is at least equal to twice the radius 30 of a central orifice of the flame stabilizer.
The flame stabilizer comprises a flange which surrounds a central opening, and which is located at the centre of the nozzle of the burner and, prefe-rably at the end of a nozzle holder for the oil.
35 It contributes to forming and stabilizing the flame.
~2~3~7 The flame stabilizer which projects radially with respect to the central nozzle-holder for the oil, thus procures a sufficient radial distance from the other annular openings for the primary air and/or other fuels which are located radially outside the flame stabilizer.
The radii of the central opening of the flame stabilizer and of the annular orifice for the principal stream of primary air located more to the inside are chosen, with the result that the inner stream of primary air lies at a distance from the centre of the nozzle which corresponds to at least double the central opening of the flame stabilizer. In this way, the central opening of the flame stabilizer corresponds substantially to the orifice of the nozzle of the central fuel conduit.
In this way, the fuel issuing centrally does not come into contact too soon with the oxygen of the principal streams of primary air.
In addition, in the preferred embodiment of the invention, there is provided in addition an annular conduit for a solid and/or gaseous fuel, disposed radially inside the primary air conduit and radially outside the flame stabilizer.
The expression "primary air conduit" generally refers to the major part of the primary air which is supplied axially or in eddying form and must not cover the small proportion of primary air (central air) which is supplied in the central zone of the flame to avoid the rearward return of the combustion products.
For the supply of this latter small proportion of primary air, according to the invention, openings are provided in the flame stabilizer, outside the central opening-2~2~7 The circulation of this small part oE primary air takes place in an annular conduit included between the central support of the oil nozzle and the following inner wall in radial direction for another admission of fuel or for one of the principal streams of primary air.
In addition, it is advantageous if the outlet opening for the axial air stream lies as far to the outside as possible in the radial direction and if it presents, furthermore, an axially projecting outer edge.
This outer ring contributes to a better constancy of the axial direction of the air, with the result that combustion is improved and the flame is stabilized.
lS According to the invention, the annular conduits for supplying primary air and~or solid or gaseous fuel, have conical walls and these walls as well as the concentric tubes connected -thereto are axially displaceable with respect to one another, so that the free transverse section of the annular passage can thus be adjusted.
However, the ends of each conduit are preferably cylindrical in order to avoid a divergent flow parallel to the direction of the conical walls.
According to the invention, in the conical part of the annular conduit for the axial air, radial partitions are disposed, intended for the axial orienta-~ tion and for the circulation of the primary air in separate channels, which are disposed on a ring and which extend essentially in axial direction.
These partitions contribute to an additional axial orientation of the corresponding primary air and also increase the axial outlet velocity, in that they reduce the free section of the annular conduit and they divide it into a plurality of individual -7- 2~
channels disposed all around a ring. Moreover, in a preferred embodiment of the invention, some of these channels are closed at least partly or are adjustable. To that end, the partitions may for example be made sufficiently wide in peripheral direction to obturate a channel at least partly or they corres-pond to a closed channel.
It is thus possible to obtain that the sum of the free sections of the channels be less than the transverse section of the annular conduit for the primary air flowing in axial direction.
As has already been explained, the axial flow velocity of the air is thus increased, which further contributes to stabilizing the flame.
In addition, according to the invention, the flame stabilizer is provided to be offset rearwardly in axial direction with respect to the openings for outlet of the principal part of the primary air and the solid or gaseous fuels. This may be effected for example by ~ixing the flame stabilizer to the tube enveloping the pipe of -the burner, which is axially displaceable, which tube is consequently offset axially.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which:
Figure 1 is an overall view of a burner with part of the supply installations.
Figure 2a is a longitudinal section through a first embodiment of a burner nozzle.
Figure 2b is a partial left-hand view of Figure 2a.
Figure 3 is a longitudinal section through another embodiment of a burner nozzle with possibility of , . .
-8- 202~7 supplying pulverized solid fuels.
Figure 4 is a longitudinal section through a burner nozzle with additional possibility of supplying a gaseous fuel.
Figure 5 is a longitudinal section through a burner nozzle with additional possibility of supplying a solid fuel and a gaseous fuel.
DETAILED DESCRIP~ION OF THE DRAWINGS
Keferring now to the drawings, Figure 1 shows a burner nozzle 1 placed at the end of an outer burner tube 5", which is at the same time the outer wall of a conduit 5' for primary air which flows in axial direction.
At the other end of the outer tube 5", different supply devices are fixed or connected by flanges.
The axial air arrives via a tube 25, the eddying air arrives via a tube 24, and these two primary air parts are adjustable separately by respective valves 45 and 44 and are connected to the same princi-pal primary air conduit. At the rear end of the burner shown in Figure 1, a conduit 22 branches from this principal prima~y air conduit and this branch termi-nates in a tube which concentrically surrounds the tube enveloping the burner pipe 10'.
In this way, a small part of the primary air coming from *he branch 22 flows through an annular conduit 11' and issues through openings 13 (cf. Figure 2b) in the central zone of the flame. A liquid fuel such as oil is supplied centrally to the nozzle of the burner via conduit 21.
A tube 23, which is intended for supplying pulve-rized solid fuels, generally powdered coal, is connec-ted to the annular conduit 15' visible in Figures 3 and 5.
~ o ~
supplying pulverlzed solid fuels.
Figure 4 is a longitudinal section through a burner nozzle with additional possibility of supplying a gaseous fuel.
Figure 5 is a longitudinal section through a burner nozzle with additional possibility of supplying a solid fuel and a gaseous fuel.
DETAILED DESCRIPTION OF TH~ DRAWINGS
Referring now to the drawings, Figure 1 shows a burner nozzle 1 placed at the end of an outer burner tube 5", which is at the same time the outer wall of a conduit 5' for primary air which flows in axial direction.
At the other end of the outer tube 5", different supply devices are fixed or connected by flanges.
The axial air arrives via a tube 25, the eddying air arrives via a tube 24, and these two primary air parts are adjustable separately by respective valves 45 and 44 and are connected to the same princi-pal primary air conduit. At the rear end of the burner shown in Figure 1, a conduit 22 branches from this principal primary air conduit and this branch termi-nates in a tube which concentrically surrounds the tube enveloping the burner pipe 10'.
In this way, a small part of the primary air coming from the branch 22 flows through an annular conduit 11' and issues through openings 13 (cf. Figure 2b) in the central zone of the flame. A liquid fuel such as oil is supplied centrally to the nozzle of the burner via conduit 21.
A tube 23, which is intended for supplying pulve-rized solid fuels, generally powdered coal, is connec-ted to the annular conduit 15' visible in Figures 3 and 5.
g The concentric tubes 10", 11", 4", 5", 15" and 19", which are engaged in one another, have different lengths. The innermost tubes project axially towards the rear beyond the outermost tubes, with the result that, as shown in Figure 1, adjusting devices 33, 34, 35 may be positioned which allow a relative axial displacement of the tubes with respect to one another.
To that end, the individual tubes are connected to one another by means of deformable gussets.
A monitoring unit 30 serves to monitor and control the streams of primary air.
Figure 2a shows a longitudinal section and Figure 2b a partial front view of a burner nozzle which is designed to operate exclusively with a fuel, for example oil, arriving at the centre.
The flame stabilizer 3, which is located at the end of tube 10', which envelops the nozzle-holder pipe of the oil burner and which projects radially with respect to the opening of the nozzle, guarantees that the opening 4 of the annular supply conduit along 4' opens out at a considerable radial distance from the central opening 2 of the fIame stabilizer.
In the embodiment shown, the radial distance D of the annular opening 4 with respect to the axis of the burner is more than triple the radius d of the opening 2. The corresponding distances are indica-ted in Figure 4, in which the ratio D/d is even greater.
~ The zone located essentially in front of the flame stabilizer constitutes a central dead zone 20, which is located outside the central fuel stream and clearly within the principal admission of primary air issuing from the annular openings 4 and 5.
This dead zone may extend axially up to a multiple of the diameter of the flame stabilizer. A mixture of the primary combustion air and of the fuel suffi-'~2~
cient for the formation of a flame is produced only outside this central dead zone. The flame stabilizer 3 comprises a hub in the form of a flange surrounding a central orifice 2. This hub comprises small openings 13. The outer face of the hub, i.e. the front face, bears fins 12 which guide the small proportion of primary air issuing from openings 13.
The outer supply conduit 5' comprises at its end conical walls 6 which diverge outwardly. In the 10 zone of these walls 6 are located juxtaposed partitions 6' which have a longitudinal section of triangular shape. These triangular walls are juxtaposed along a common side which is parallel to the axis of the burner and which is placed at the same radial distance 15 from this axis as the outer wall of the conduit 5'.
In this way, it is possible to displace the tube 4" axially with respect to tube 5" without the function of partitions 6' being influenced thereby.
Figure 2b shows a front view of the front edges 20 Of the partitiOnS 6'.
However, partitions 6' may also have, in periphe-ral direction, a sufficient width for them to corres-pond to the parts located between the channels 5 shown in Figure 2. These parts may also be considered as closed channels 5.
The supply conduit 4' comprises in front of the conical end, a device 14 for eddying the air, i.e. for setting it in rotation about the axis of the burner. This device is essentially con5tituted by fins for guiding the air which are oriented oblique-ly with respect to the axis of the burner.
Thanks to the axial displacement of tube 11' with respect to tube 4', the distance between the conical walls 7 of conduit 4' may be varied, with the result that the transverse section of conduit --ll--4' may thus be modified. The terminal part of conduit 4' in the zone of opening 4 is, however, again cylin-drical in order to avoid a divergent flow of the eddying air lssuing from this opening.
Similarly, edge 8, which projects forwardly in axial direction, procures an axial outlet direction of the axial air stream.
In connection with the outlet direction and the acceleration of the axial air in conduit 5, this guarantees an axial air flow which is stable, uniform and of broad scope.
Figure 3 shows an embodiment of the burner nozzle which differs from the embodiment shown in Figure 2, essentially by the presence of an additional conduit 1~ 15', for powdered solid fuels, which is located between the flame stabilizer 3 and the conduit 4' of eddying primary air.
It is generally question of powdered coal which is transported in the burner by a vector gas, for 20 example air. Due to the abrasive properties of such a solid fuel, the terminal zone of conduit 15' is only slightly conical in order to allow passage of the fuel which is as easy as possible.
Figure 4 shows an embodiment comprising, in 25 place of conduit 15' ~or a solid fuel, another conduit 19' for a gaseous fuel, whose terminal section may be conical, like conduit 4', and which may also com-prise a device for eddying the gas issuing from this conduit. In that case too, the terminal section of 30 conduit 19' is cylindrical in the zone of opening 19, in order to avoid a divergence of the gaseous fuel which issues therefrom.
Figure 5 shows an embodiment which comprises both a supply conduit 15' for solid fuels and a conduit 35 19' for gaseous fuels.
2 ~ 7 Conduits 4' and 5' for the principal proportion of primary air in the form of eddying air and air having an axial direction are disposed outside these two fuel conduits in radial direction. The inner edge of the opening 15, by which a considerable part of the primary combustion air may penetrate in the burner in the form of vector gas for the solid fuel, is located at a distance D' from the axis of the burner, which is more than double the radius d of the opening 2 of the flame stabilizer, with the result that, in all cases, the existence is guaranteed at the centre of the flame of a sufficiently large dead zone which procures the advantageous properties of the present invention.
Thanks to the invention, a burner and a process for exploiting a buxner equipping a rotary tube furnace have been created, which allow a reduced proportion of primary air and a broader range of adjustment of the burner, this leading to reduced energy consump-tion and a reduction of the formation of nitrogenoxides detrimental to the environment.
The present invention relates to a process for exploitation of a burner for a rotary tube furnace, in which fuels and primary air are supplied concentri-cally.
The present invention also relates to a burnerfor a rotary tube furnace equipped with a burner nozzle fitted with fuel and primary air conduits whlch are disposed substantially concentrically with 10 respect to one another, which primary air includes air set in rotation and air flowing axially.
BACKGROUND OF THE INVENTION
A burner of this type is disclosed in German Patent DE 2 905 746.
This known burner comprises, in addition to a central fuel admission for the oil, another fuel admission disposed concentrically thereto for powdered coal or any other like fuel.
For the purpose of obtaining a good mixture, 20 this solid fuel admission lies between two streams of primary air, of which one, which is the central stream, is set in rotation or eddy, i.e. it comprises a component in tangential or peripheral direction, and of which the other, outer, stream comprises an essentially axial flow velocity for the purpose of stabilizing the flame which penetrates far in the rotary furnace.
In other known burners, the stream of primary air is also provided to extend relatively far in the interior.
The known burner comprises, at its centre, a liquid fuel, generally oil, admission. The liquid fuel is atomized into fine droplets by means of a spray nozzle and is mixed, after leaving the central opening of the nozzle, with primary air which issues from the opening for outlet of eddying air, which opening is located radially around the central opening.
The known burners are usually employed with a proportion of primary air of between 8~ and 25%
of the total quantity of combustion air.
The power of the burner, i.e. the operational working, is regulated by a respective reduction or increase of the fuel and the air admission within a determined range of adjustment, in which the minimum adjustable working for obtaining a stable flame is equal to about 20 to 25~ of the maximum working pos-sible.
When the burner is started, oil must, as a general rule, be injected through the central orifice of the nozzle and must be ignited in order to pre-heat the furnace, since combustion of the solid fuel, which is supplied concentrically, is possible only in a sufficiently pre-heated furnace.
With respect to this state of the art, the present invention has for its object to provide a process for exploiting a burner of a rotary tube furnace and also a burner adapted to carry out this process, which may operate with a smaller proportion of primary air and present a broader range of adjustment of the operational working.
SUMMARY OF THE INVENTION
As far as the process is concerned, this object is attained by providing directly all around a central fuel supply conduit and/or radially inside an annular fuel supply conduit, a central dead zone in which, at the most, a reduced proportion of the primary combustion air is sent.
Thanks to the presence of a central dead zone, combustion thus begins at a greater distance in front of the centre of the nozzle of the burner compared 2~2~
3_ with the heretofore known processes and burners.
In this way, seen in longitudinal section, star-ting from the centre of the front end of the nozzle, the resultant f]ame comprises a central zone which S extends forwardly and radially, in which virtually no noteworthy combustion of the fuel is produced with the oxygen of the air.
It is true that such a central flame heart is also present in principle in the known burners, whilst, according to the present invention, this central dead zone is provoked deliberately and enlarged, more particularly by the fact that the least primary air possible is supplied in this zone.
However, even if it is not provided in the first place for combustion, a small proportion of primary air may be supplied in this central zone, this small proportion of primary air serving, however, in the first place to stabilize the flame and to prevent a rearward return of the combustion gases, the coal ash and the coke, which, without that, would lead to the soiling of the central part of the nozzle.
A small stream of primary air in this central zone, which is below 20% and preferably below 10%
of the total primary air, avoids such a rearward return of the combustion products, without supplying much oxygen which would reduce the central zone rich in fuel.
It has been unexpectedly found that, thanks to the presence of such enlarged central dead zone, the range of adjustment of the burner may be conside-rably increased, up to less than 10% of the maximum working for which the burner is designed.
Insofar as such a burner must operate especially with solid and pulverized fuels, this means that, after a brief pre-heating with oil, it may already 2~3~7 function with the solid fuel.
At the same time, it has been shown that, in such a process and in a burner designed for this process, the proportion of primary air which must be used for stabilizing the flame may be reduced by 2 to 10% and preferably below 6% with respect to the overall quantity of combustion air. This facili-tates manufacture of the primary air supply devices which may be designed respectively weaker.
A particular advantage of the reduced consumption of primary air resides in the resulting saving of energy for an equal performance and also in the reduc-tion of the proportion of nitrogen oxides in the combustion gases.
According to the invention, it is provided that, separately from the introduction of a small proportion of primary air in the central zone, at least two other separate streams of primary air are supplied, one of which is essentially axial and the other has 20 a major part of the flow components in peripheral direction.
As far as the device mentioned above is concerned, the object of the invention is attained by locating the orifices for admission of the eddying air and 25 of the axial air, outside the orifices for admission of the fuel, and the minimum radial distance with respect to the centre of the nozzle of the burner - from the outlet orifices for the eddying air and the axial air, is at least equal to twice the radius 30 of a central orifice of the flame stabilizer.
The flame stabilizer comprises a flange which surrounds a central opening, and which is located at the centre of the nozzle of the burner and, prefe-rably at the end of a nozzle holder for the oil.
35 It contributes to forming and stabilizing the flame.
~2~3~7 The flame stabilizer which projects radially with respect to the central nozzle-holder for the oil, thus procures a sufficient radial distance from the other annular openings for the primary air and/or other fuels which are located radially outside the flame stabilizer.
The radii of the central opening of the flame stabilizer and of the annular orifice for the principal stream of primary air located more to the inside are chosen, with the result that the inner stream of primary air lies at a distance from the centre of the nozzle which corresponds to at least double the central opening of the flame stabilizer. In this way, the central opening of the flame stabilizer corresponds substantially to the orifice of the nozzle of the central fuel conduit.
In this way, the fuel issuing centrally does not come into contact too soon with the oxygen of the principal streams of primary air.
In addition, in the preferred embodiment of the invention, there is provided in addition an annular conduit for a solid and/or gaseous fuel, disposed radially inside the primary air conduit and radially outside the flame stabilizer.
The expression "primary air conduit" generally refers to the major part of the primary air which is supplied axially or in eddying form and must not cover the small proportion of primary air (central air) which is supplied in the central zone of the flame to avoid the rearward return of the combustion products.
For the supply of this latter small proportion of primary air, according to the invention, openings are provided in the flame stabilizer, outside the central opening-2~2~7 The circulation of this small part oE primary air takes place in an annular conduit included between the central support of the oil nozzle and the following inner wall in radial direction for another admission of fuel or for one of the principal streams of primary air.
In addition, it is advantageous if the outlet opening for the axial air stream lies as far to the outside as possible in the radial direction and if it presents, furthermore, an axially projecting outer edge.
This outer ring contributes to a better constancy of the axial direction of the air, with the result that combustion is improved and the flame is stabilized.
lS According to the invention, the annular conduits for supplying primary air and~or solid or gaseous fuel, have conical walls and these walls as well as the concentric tubes connected -thereto are axially displaceable with respect to one another, so that the free transverse section of the annular passage can thus be adjusted.
However, the ends of each conduit are preferably cylindrical in order to avoid a divergent flow parallel to the direction of the conical walls.
According to the invention, in the conical part of the annular conduit for the axial air, radial partitions are disposed, intended for the axial orienta-~ tion and for the circulation of the primary air in separate channels, which are disposed on a ring and which extend essentially in axial direction.
These partitions contribute to an additional axial orientation of the corresponding primary air and also increase the axial outlet velocity, in that they reduce the free section of the annular conduit and they divide it into a plurality of individual -7- 2~
channels disposed all around a ring. Moreover, in a preferred embodiment of the invention, some of these channels are closed at least partly or are adjustable. To that end, the partitions may for example be made sufficiently wide in peripheral direction to obturate a channel at least partly or they corres-pond to a closed channel.
It is thus possible to obtain that the sum of the free sections of the channels be less than the transverse section of the annular conduit for the primary air flowing in axial direction.
As has already been explained, the axial flow velocity of the air is thus increased, which further contributes to stabilizing the flame.
In addition, according to the invention, the flame stabilizer is provided to be offset rearwardly in axial direction with respect to the openings for outlet of the principal part of the primary air and the solid or gaseous fuels. This may be effected for example by ~ixing the flame stabilizer to the tube enveloping the pipe of -the burner, which is axially displaceable, which tube is consequently offset axially.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which:
Figure 1 is an overall view of a burner with part of the supply installations.
Figure 2a is a longitudinal section through a first embodiment of a burner nozzle.
Figure 2b is a partial left-hand view of Figure 2a.
Figure 3 is a longitudinal section through another embodiment of a burner nozzle with possibility of , . .
-8- 202~7 supplying pulverized solid fuels.
Figure 4 is a longitudinal section through a burner nozzle with additional possibility of supplying a gaseous fuel.
Figure 5 is a longitudinal section through a burner nozzle with additional possibility of supplying a solid fuel and a gaseous fuel.
DETAILED DESCRIP~ION OF THE DRAWINGS
Keferring now to the drawings, Figure 1 shows a burner nozzle 1 placed at the end of an outer burner tube 5", which is at the same time the outer wall of a conduit 5' for primary air which flows in axial direction.
At the other end of the outer tube 5", different supply devices are fixed or connected by flanges.
The axial air arrives via a tube 25, the eddying air arrives via a tube 24, and these two primary air parts are adjustable separately by respective valves 45 and 44 and are connected to the same princi-pal primary air conduit. At the rear end of the burner shown in Figure 1, a conduit 22 branches from this principal prima~y air conduit and this branch termi-nates in a tube which concentrically surrounds the tube enveloping the burner pipe 10'.
In this way, a small part of the primary air coming from *he branch 22 flows through an annular conduit 11' and issues through openings 13 (cf. Figure 2b) in the central zone of the flame. A liquid fuel such as oil is supplied centrally to the nozzle of the burner via conduit 21.
A tube 23, which is intended for supplying pulve-rized solid fuels, generally powdered coal, is connec-ted to the annular conduit 15' visible in Figures 3 and 5.
~ o ~
supplying pulverlzed solid fuels.
Figure 4 is a longitudinal section through a burner nozzle with additional possibility of supplying a gaseous fuel.
Figure 5 is a longitudinal section through a burner nozzle with additional possibility of supplying a solid fuel and a gaseous fuel.
DETAILED DESCRIPTION OF TH~ DRAWINGS
Referring now to the drawings, Figure 1 shows a burner nozzle 1 placed at the end of an outer burner tube 5", which is at the same time the outer wall of a conduit 5' for primary air which flows in axial direction.
At the other end of the outer tube 5", different supply devices are fixed or connected by flanges.
The axial air arrives via a tube 25, the eddying air arrives via a tube 24, and these two primary air parts are adjustable separately by respective valves 45 and 44 and are connected to the same princi-pal primary air conduit. At the rear end of the burner shown in Figure 1, a conduit 22 branches from this principal primary air conduit and this branch termi-nates in a tube which concentrically surrounds the tube enveloping the burner pipe 10'.
In this way, a small part of the primary air coming from the branch 22 flows through an annular conduit 11' and issues through openings 13 (cf. Figure 2b) in the central zone of the flame. A liquid fuel such as oil is supplied centrally to the nozzle of the burner via conduit 21.
A tube 23, which is intended for supplying pulve-rized solid fuels, generally powdered coal, is connec-ted to the annular conduit 15' visible in Figures 3 and 5.
g The concentric tubes 10", 11", 4", 5", 15" and 19", which are engaged in one another, have different lengths. The innermost tubes project axially towards the rear beyond the outermost tubes, with the result that, as shown in Figure 1, adjusting devices 33, 34, 35 may be positioned which allow a relative axial displacement of the tubes with respect to one another.
To that end, the individual tubes are connected to one another by means of deformable gussets.
A monitoring unit 30 serves to monitor and control the streams of primary air.
Figure 2a shows a longitudinal section and Figure 2b a partial front view of a burner nozzle which is designed to operate exclusively with a fuel, for example oil, arriving at the centre.
The flame stabilizer 3, which is located at the end of tube 10', which envelops the nozzle-holder pipe of the oil burner and which projects radially with respect to the opening of the nozzle, guarantees that the opening 4 of the annular supply conduit along 4' opens out at a considerable radial distance from the central opening 2 of the fIame stabilizer.
In the embodiment shown, the radial distance D of the annular opening 4 with respect to the axis of the burner is more than triple the radius d of the opening 2. The corresponding distances are indica-ted in Figure 4, in which the ratio D/d is even greater.
~ The zone located essentially in front of the flame stabilizer constitutes a central dead zone 20, which is located outside the central fuel stream and clearly within the principal admission of primary air issuing from the annular openings 4 and 5.
This dead zone may extend axially up to a multiple of the diameter of the flame stabilizer. A mixture of the primary combustion air and of the fuel suffi-'~2~
cient for the formation of a flame is produced only outside this central dead zone. The flame stabilizer 3 comprises a hub in the form of a flange surrounding a central orifice 2. This hub comprises small openings 13. The outer face of the hub, i.e. the front face, bears fins 12 which guide the small proportion of primary air issuing from openings 13.
The outer supply conduit 5' comprises at its end conical walls 6 which diverge outwardly. In the 10 zone of these walls 6 are located juxtaposed partitions 6' which have a longitudinal section of triangular shape. These triangular walls are juxtaposed along a common side which is parallel to the axis of the burner and which is placed at the same radial distance 15 from this axis as the outer wall of the conduit 5'.
In this way, it is possible to displace the tube 4" axially with respect to tube 5" without the function of partitions 6' being influenced thereby.
Figure 2b shows a front view of the front edges 20 Of the partitiOnS 6'.
However, partitions 6' may also have, in periphe-ral direction, a sufficient width for them to corres-pond to the parts located between the channels 5 shown in Figure 2. These parts may also be considered as closed channels 5.
The supply conduit 4' comprises in front of the conical end, a device 14 for eddying the air, i.e. for setting it in rotation about the axis of the burner. This device is essentially con5tituted by fins for guiding the air which are oriented oblique-ly with respect to the axis of the burner.
Thanks to the axial displacement of tube 11' with respect to tube 4', the distance between the conical walls 7 of conduit 4' may be varied, with the result that the transverse section of conduit --ll--4' may thus be modified. The terminal part of conduit 4' in the zone of opening 4 is, however, again cylin-drical in order to avoid a divergent flow of the eddying air lssuing from this opening.
Similarly, edge 8, which projects forwardly in axial direction, procures an axial outlet direction of the axial air stream.
In connection with the outlet direction and the acceleration of the axial air in conduit 5, this guarantees an axial air flow which is stable, uniform and of broad scope.
Figure 3 shows an embodiment of the burner nozzle which differs from the embodiment shown in Figure 2, essentially by the presence of an additional conduit 1~ 15', for powdered solid fuels, which is located between the flame stabilizer 3 and the conduit 4' of eddying primary air.
It is generally question of powdered coal which is transported in the burner by a vector gas, for 20 example air. Due to the abrasive properties of such a solid fuel, the terminal zone of conduit 15' is only slightly conical in order to allow passage of the fuel which is as easy as possible.
Figure 4 shows an embodiment comprising, in 25 place of conduit 15' ~or a solid fuel, another conduit 19' for a gaseous fuel, whose terminal section may be conical, like conduit 4', and which may also com-prise a device for eddying the gas issuing from this conduit. In that case too, the terminal section of 30 conduit 19' is cylindrical in the zone of opening 19, in order to avoid a divergence of the gaseous fuel which issues therefrom.
Figure 5 shows an embodiment which comprises both a supply conduit 15' for solid fuels and a conduit 35 19' for gaseous fuels.
2 ~ 7 Conduits 4' and 5' for the principal proportion of primary air in the form of eddying air and air having an axial direction are disposed outside these two fuel conduits in radial direction. The inner edge of the opening 15, by which a considerable part of the primary combustion air may penetrate in the burner in the form of vector gas for the solid fuel, is located at a distance D' from the axis of the burner, which is more than double the radius d of the opening 2 of the flame stabilizer, with the result that, in all cases, the existence is guaranteed at the centre of the flame of a sufficiently large dead zone which procures the advantageous properties of the present invention.
Thanks to the invention, a burner and a process for exploiting a buxner equipping a rotary tube furnace have been created, which allow a reduced proportion of primary air and a broader range of adjustment of the burner, this leading to reduced energy consump-tion and a reduction of the formation of nitrogenoxides detrimental to the environment.
Claims (15)
- WHAT IS CLAIMED IS:
l. A process for exploitation of a burner for rotary tube furnaces, in which fuels and primary combustion air are supplied concentrically, wherein there is provided directly all around a central fuel supply conduit and/or radially inside an annular fuel supply conduit, a central dead zone in which at the most a reduced proportion of primary combustion air is sent. - 2. The process of Claim 1, wherein the percentage of primary combustion air sent into said central dead zone is less than 20% and; preferably, than 10% of the total primary combustion air, possibly including the air used as vector gas for solid fuels.
- 3. The process of Claim 1, wherein at least two other streams of primary combustion air are sent into the burner, of which one has an essentially axial direction and of which the other has, to a large extent, flow components in peripheral direction, which streams are separated from the supply of primary air sent into said central dead zone.
- 4. The process of Claim l, wherein the proportion of primary combustion air is included between 2%
and 10% of the total combustion air and, preferably, less than 6%. - 5. In a burner for a rotary tube furnace, of the type comprising a burner nozzle, equipped with substan-tially concentric fuel supply conduits and primary combustion air conduits comprising axial air and eddying air, the outlet orifices for the eddying air and the axial air are disposed radially outside the outlet openings for the fuels and the minimum radial distance of said outlet openings for the major part of the primary air with respect to the centre of the nozzle of the burner, is at least twice the radius of the central opening of a flame stabilizer.
- 6. The burner of Claim 5, comprising an annular outlet opening for solid and/or gaseous fuels, which is located radially inside the outlet openings for the eddying primary air and the axial air and outside the flame stabilizer.
- 7. The burner of Claim 5, wherein the flame stabi-lizer is disposed at the front end of a central oil nozzle-holder.
- 8. The burner of Claim 5, wherein the flame stabi-lizer comprises openings for the passage of a small part of the primary combustion air, which are located outside the central opening.
- 9. The burner of Claim 5, wherein the outlet opening for axial air is located radially as far to the outside as possible and comprises an outer edge which projects axially towards the front.
- 10. The burner of Claim 5, wherein the annular supply conduits present, upstream of their outlet opening, conical wall portions which are axially displaceable with respect to one another.
- 11. The burner of Claim 10, wherein at, least certain of the annular supply conduits comprise a cylindrical terminal portion of at least one wall of each of said supply conduits, which is located between the conical wall portion and the annular outlet opening.
- 12. The burner of Claim 9, wherein the annular channel for the axial air comprises, in the conical zone, partitions for the supply and axial orientation of the primary air in separate channels, disposed in a ring and extending axially.
- 13. The burner of Claim 12, wherein the section of the annular passage for the axial air or the corres-ponding channels disposed in a ring are at least in part closed or adapted to be obturated.
- 14. The burner of Claim 12, wherein the sum of the sections of free passage of the axial channels is substantially smaller than the section of the annular conduit for the primary air flowing in axial direction.
- 15. The burner of Claim 5, wherein the flame stabi-lizer is offset axially to the rear with respect to the outlet openings for the eddying air, the axial air and/or for the solid or gaseous fuels.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3933050A DE3933050C2 (en) | 1989-10-04 | 1989-10-04 | Method for operating a burner for rotary kilns and burners therefor |
| DEP3933050.8 | 1989-10-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2026857A1 true CA2026857A1 (en) | 1991-04-05 |
Family
ID=6390771
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002026857A Abandoned CA2026857A1 (en) | 1989-10-04 | 1990-10-03 | Process for exploiting a burner and burners for a rotary tubular furnace |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0421903B2 (en) |
| AT (1) | ATE115706T1 (en) |
| CA (1) | CA2026857A1 (en) |
| DE (1) | DE3933050C2 (en) |
| DK (1) | DK0421903T3 (en) |
| ES (1) | ES2066179T5 (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19504667B4 (en) * | 1995-02-13 | 2005-01-05 | Schwenk Zement Kg | Burner system for cement kilns |
| DK173204B1 (en) | 1997-03-07 | 2000-03-13 | F.L.Smidth & Co A/S | is in an oven Proceed and burn to introduce burning |
| FR2772887B1 (en) | 1997-12-24 | 2000-03-17 | Pillard Chauffage | LOW-EMISSION NITROGEN OXIDE BURNER WITH RECYCLED GAS CIRCUIT |
| FR2772888B1 (en) * | 1997-12-24 | 2000-03-10 | Pillard Chauffage | IMPROVEMENT TO SOLID FUEL BURNERS |
| FR2780489B1 (en) * | 1998-06-24 | 2000-09-08 | Pillard Chauffage | IMPROVEMENT IN BURNERS COMPRISING AT LEAST THREE AIR SUPPLY DUCTS, OF WHICH TWO AXIAL AND ROTATING, CONCENTRIC WITH AT LEAST ONE FUEL-SUPPLY, AND A CENTRAL STABILIZER |
| FR2792393B1 (en) * | 1999-04-16 | 2001-06-29 | Pillard Chauffage | MULTI-FUEL BURNER |
| FR2803022A1 (en) | 1999-12-28 | 2001-06-29 | Pillard Chauffage | Pulverised solid fuel burner air feed uses part of air after purification for additional primary combustion and flame regulation |
| IT1316825B1 (en) * | 2000-03-22 | 2003-05-12 | Italcementi Spa | DEVICE FOR THE INJECTION OF SOLID FUELS INTO DUST FORMED IN A CONCRETE OVEN |
| US6315551B1 (en) | 2000-05-08 | 2001-11-13 | Entreprise Generale De Chauffage Industriel Pillard | Burners having at least three air feed ducts, including an axial air duct and a rotary air duct concentric with at least one fuel feed, and a central stabilizer |
| FR2823290B1 (en) | 2001-04-06 | 2006-08-18 | Air Liquide | COMBUSTION PROCESS INCLUDING SEPARATE INJECTIONS OF FUEL AND OXIDIZING AND BURNER ASSEMBLY FOR IMPLEMENTATION OF THIS PROCESS |
| DE10140422C1 (en) * | 2001-08-17 | 2002-11-28 | Eisenmann Kg Maschbau | Thermal post-combustion device for cleaning waste gases comprises a burner having a second flame tube surrounding the end of a first flame tube with a greater radius to form an annular gap |
| FR2851032B1 (en) * | 2003-02-06 | 2005-11-11 | Pillard Chauffage | BURNER IMPROVEMENT COMPRISING A FLAME STABILIZER AND AT LEAST TWO PRIMARY, AXIAL AND ROTATING AIR DUCTS, CONCENTRIC AROUND AT LEAST ONE FUEL SUPPLY |
| FR2919043A1 (en) * | 2007-07-20 | 2009-01-23 | Pillard Chauffage | BURNER COMPRISING AN ANNULAR AIR SUPPLY PIPE |
| FR2930626B1 (en) * | 2008-04-28 | 2010-05-21 | Fives Pillard | BURNER WITH PERIPHERAL AIR FLOW INJECTION POINTS |
| DE202008009650U1 (en) * | 2008-07-18 | 2009-11-26 | Ammann Schweiz Ag | Multi-fuel burner |
| CN106568081A (en) * | 2016-11-03 | 2017-04-19 | 扬州新建水泥技术装备有限公司 | Novel burner |
| CN113203283B (en) * | 2021-04-26 | 2022-04-22 | 中国科学院力学研究所 | Oxygen-enriched air shovel type kiln head staged combustion device and method for rotary cement kiln |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE7904137U1 (en) * | 1979-02-15 | 1982-09-30 | Pillard Feuerungen GmbH, 6204 Taunusstein | BURNER FOR POWDER-SHAPED OR FINE-GRAINED SOLID FUELS AND COMBINATIONS OF SOLID, LIQUID AND / OR GASEOUS FUELS FOR THE MOST POSSIBLE ADJUSTMENT OF THE FLAME SHAPE, DURING OPERATION |
| CA1204999A (en) * | 1981-04-08 | 1986-05-27 | Edward J. Campobenedetto | Low nox multifuel burner |
-
1989
- 1989-10-04 DE DE3933050A patent/DE3933050C2/en not_active Expired - Lifetime
-
1990
- 1990-09-14 DK DK90430017.5T patent/DK0421903T3/en active
- 1990-09-14 ES ES90430017T patent/ES2066179T5/en not_active Expired - Lifetime
- 1990-09-14 EP EP90430017A patent/EP0421903B2/en not_active Expired - Lifetime
- 1990-09-14 AT AT90430017T patent/ATE115706T1/en not_active IP Right Cessation
- 1990-10-03 CA CA002026857A patent/CA2026857A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| ES2066179T5 (en) | 1999-01-01 |
| EP0421903A2 (en) | 1991-04-10 |
| DK0421903T3 (en) | 1995-05-15 |
| DE3933050C2 (en) | 2000-06-15 |
| EP0421903B1 (en) | 1994-12-14 |
| EP0421903B2 (en) | 1998-09-23 |
| DE3933050A1 (en) | 1991-04-11 |
| ES2066179T3 (en) | 1995-03-01 |
| EP0421903A3 (en) | 1991-10-02 |
| ATE115706T1 (en) | 1994-12-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |