CA1145659A - Burner - Google Patents
BurnerInfo
- Publication number
- CA1145659A CA1145659A CA000359729A CA359729A CA1145659A CA 1145659 A CA1145659 A CA 1145659A CA 000359729 A CA000359729 A CA 000359729A CA 359729 A CA359729 A CA 359729A CA 1145659 A CA1145659 A CA 1145659A
- Authority
- CA
- Canada
- Prior art keywords
- air
- tube
- burner
- nozzles
- mantle
- 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.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE
A burner for combustion of nitrogen-containing fuels.
The burner comprises a core-air tube with centrally arranged oil atomizing lance, a dust tube surrounding the core-air tube, a mantle-air tube which surrounds the dust tube and is provided with an axially shiftable twist-blade ring ar-ranged at the air inlet, as well as a burner opening which expands conically toward the combustion chamber. The core-air tube and the mantle-air tube are supplied from a main air conduit. Air jets or nozzles are provided in a con-centric arrangement around the burner opening. These air nozzles are connected with the main air passage by con-duits, and the air stream discharging from the air nozzles is regulated by a flap.
A burner for combustion of nitrogen-containing fuels.
The burner comprises a core-air tube with centrally arranged oil atomizing lance, a dust tube surrounding the core-air tube, a mantle-air tube which surrounds the dust tube and is provided with an axially shiftable twist-blade ring ar-ranged at the air inlet, as well as a burner opening which expands conically toward the combustion chamber. The core-air tube and the mantle-air tube are supplied from a main air conduit. Air jets or nozzles are provided in a con-centric arrangement around the burner opening. These air nozzles are connected with the main air passage by con-duits, and the air stream discharging from the air nozzles is regulated by a flap.
Description
, The present invention rela~es to a burner for burning nitrogen-containing fuels. The burner comprises a core-air tube having a centrally arranged oil atomizing lance, a dust tube surrouncling the core-air tube, a mantle-air tube which surrounds the dust tube and is provided with an axially shiftable twist blade ring arranged at the air inlet, as well as a burner opening which widens conically toward the combustion charnber, ~ith the core-air tube and the mantle-air tube being supplied from a main air concluit.
Burners with the aforementioned structural features generate Elames which in turn generate a considerable con-centration of NO~ in the flue gases. The reaction mechanisms causing the formation o~ nitrogen oxides in teclmical com-bustion are mostly Icnown. ~* the prcscnt, thc!re are essen-tially two dlfferent fornlation reac~ions as follows:
(1) 'rhe thermic NOX formatioll, which is l>asecl upon oxidation oE molecular nitrogen, ~hich occurs or instance amply in the combustion air. Since the oxidation o molecular nitrogen requires atomic oxygen or aggressive radicals (or instance OEI, 03, etc.), such o~idation is strongly depenclent upon temperature, thus thermic NO~; and ~ 2) the formation of fuel NOX, which occurs by o~i-dation of nitrogen compounds bound in the fuel. During the pyrolysis, nitrogen-carbon and nitro~en-hydrogen radicals (CH, HCN, CH, etc.) form Erom these nitrogen compounds. These radicals oxidize to form NO~ already at ~' ~ ~ ~ 5~ ~
relatively low temperatures in the presence of o~ygen be-cause of their reactivity with molecular oxygen.
A reduction of the thermic N0~-formation is accordingly primarily obtained by lowering the combustion temperature and the retention times at high temperatures. Since with the combustion of fuels with bound nitrogen, however, a large portion of the tot~l N0x-fonmation results from the fuel-N0~-reaction, the a~orementioned measures with such fuels are not suficient for complying with the emi~sion standards existing in certain countries. For this purpose, it is necessary to reduce the nitrogen compounds into molecular nitrogen (N2) still during the pyrolysis in the presence of o~ygen. Tests have shown that these reduction reflctions to mo]ecular nitro-gen occur, for instance, when the fuels are burned ~t below-stoichiometrlc condi~ions, that is, with less oxygen addition or air addition than necessary Eor complete combustLon. To achieve optimtlm resul~s, an ~ir ratio between 0.9 and 0.5 is selectecl for the primary combustion ~one as a function of thc limiting or edge conditions (for instance w~ll tempernture of the combustion chamber). I-lowever, to achieve a complete com-bustion of the carbon-hydrogen compounds of the fuel, the reaction products resulting in the below-stoichiometric primary region must then be afterburned.
Tests have shown that with such a two-step com~ustion, both the fuel-N0~-formation (with simultaneous heat removal from the below-stoichiometric region) as well as the thermic N0~-formation can be considerably reduced. In tests utilizing the two-step combustion, the N0x-emission values were reduced appro~ima~ely up to 70% compared with ~m-stepped combustion.
By tests it was proven that the formation of fuel N0~
could be clearly reduced by operating the burner in the near-stoichiometric or below-stoichiometr~c range. In order to avoid losses through incomplete combustion, and co avoid in-crease of other noxious material emlssions (C0, hydrocarbons, and particles), additional air must be blo~ in above the burners in the combustion chamber during the below-stoichio-metric operation of the burners. The disadvantage o this manner of operation is that in the below-stoichiometrically operatecl lower part oE the combustion chamber sintering and corrosion of the tube wal]s can occur. Accordingly, the operational reliabi]ity o~ the system is in clanger.
It has furtherrnore been detennLnecl tha~ by slo~in~ the mixture betwee~n air ~low and fuel ~]ot~, likcwise considerable reduction o;E N0~-emission can be acllieved. For thi.s purpose, Elow or spray burnors, ~or installco, Mre suitable, ~Lth which both the air stream and thc Euel s~leam arc blown in para]lel into the combustion chamber. To achieve a satisfactory igni-tion, the burner streams must, ho~]ever, support each other, for instance in a corner firing or combustion.
With the arrangement of the burners in a front- or coun-ter-firing or combustion, the mixture of air and fuel can, for example, be slowed thereby that the secondary air surrounding 1~5~
the dust stream is blown-in at substantially the same speed.
In a known burner, the secondary air flow or stream is added separately in two tubes, which are arranged annularly with respect to each other, to permit clischarge of, for example, the inner secondary air stream, with a low speed, directly adjoining the dust stream, and of the outer secondary air stream with higher speed. Disadvantageous with this ar-rangement is that an extension of the flame occurs, which has as a consequence larger combustion chambers, and that with the load-conditioned reduction of the secondary air, the speed of the secondary air is reduced below the dust-air speed, whereby the character and shape of the flame change. The ignition could also be disadvantageous]y influenced thereby.
Furthermore, it is known to undertake a primary combus-tion at below-stoichiometric conditions in an antechamber of the combustion chamber, and to aclmix the air necessary for complete combustion with the combustLo[l gases which leave the antechamber. Thc disadvanta~e oE this arran~,ement exists in the danger o tube wall corroslon oE the antech~mber which is operated below-stoichiometric condition.
It is thereEore an object oE the present invention to develop a burner with which, by influencing the secondary air flow and introducing the same at different locations of the combustion chamber, yet always in association with the burner, the combustion is influenced in such a manner that in a pri-mary zone or partial combustion zone directly adjoining the S~'3 burner outlet there is obtained a stable ignition over the entire load range at below-stc)ichiometric condi tiOTlS ~ and in a secondary zone or afterburning ~one adjoining the pri-mary zone the remainder or balance of the combustion occurs at above-stoichiometric conditions.
This object and other objects and advantages of the present invention will appear more clearly from the follow-in~ specificat.ion in connect.ion with the accompanying draw-:ing, in which:
Figure I is a longitudinal section through a burner ~ccording to the present inventive pr:inc~ple; and I~`igtlre 2 is a view of the burner in the direction of arrow F in l~igure 1.
By one aspect o this invention, a burncr is provided for coml)ust,.ion o.E ~uel which con~nlns nitrogen, sai(i burner cornprLsi.ng: a mnin nir sllppl.y concluit; ~ core-air tube which is Ln colnmutllcat:ion wLth sald main air supply conduit;
an oil atoml~i.n~, ~lance central],y arran~ed in sai.cl core-air tube; a dust tube ~hLch sllrrouncl.s at l~ast a part oE saicl core-air tube; a mantle-lir tubc which surrouncls at least a part of sa,id clust tube and is provided with an air inlet which is in communication with said main air supply conduit, saicl mantle-air tube being connected to and in communication with a burner opening which widens conically toward a com-bustion chamber; an axially shiftable twist blade ring arranged in said air inlet of said mantle-air tube; air ~ tj~ 59 nozzles concentrically arranged around said burner opening, said air nozzles being in communication with said main air supply conduit; and a flap for regulating the air flow through said air nozzles.
In accordance with a further embodiment of the present invention, the air nozzles can be embodied as hole-type nozzles or as air jets (slotted nozzles), whereby, for in-stance, the slot-like openings are produced by removal of the fins or blades between the tubes.
In another embodiment of the present invention, it is further proposed that at least two air nozzles, with a max-imum of six air nozzles, be arranged in a divided or grad-uatecl circle, which may be ]ocated concentrically with respect to the mantle-air tube, the divicled circle diameter being at least 1.5 tlmes, with a maximum o~ 3 times, the diameter of the mantle-air tube.
The advantages obtained with the present inverlLion con-sist in that by aclding to the combustion chamber a part of the secondary air by me~ns of air nozzles located externally of the mantle-air tube of the burner, the combustion pro-cedure of the fuel, which contains nitrogen and passes to the combustion, occurs in such a manner that the N0x-values are reduced to a minimum without thereby endangering the ignition of the burner over the entire load range, without sintering and corrosion resulting on the combustion chamber tubes, and without the combustion being impaired.
~ q3 Referring now to the drawing in detail, the burner com-prises a cen~ral core-air tube 1 which is suitable for re-ceiving an oil atomizing lance 5 for ignition firing or for alternative power combustion for oil. The core-air tube 1 is connected with the main air passage or conduit 4 by the passage or conduit 2 and the flap or valve 3. The dust-air tube 6 is arranged coaxial to the core-air tube 1, and is connected to the dust conduit 8 by the dust distributing chamber 7. The dust-air tube 6 is supplied by a coal-dust tube with the dust-alr mixture for combustion. A mantle-air tube 9 is arranged coaxially around the dust-air tube 6, and is connected by flaps 13 with the main air conduit 4. A
twist-blade ring 10, through which the mantle air 10ws axially, can be shifted ~xially by several spindles 11 and the hand wheel 12. The mantle-air passa~e 9 is connected with the combus~lon chamber by the conical]y ~idening burner chalice or openlng 14. Stepped-nir nozzles or jets 1(~ are supplied with air ~rom the ~in air condui~ 4 by se-veral conduits 15. These stepped-air jets or nozzl~s 16 ~o are uniformly distributed over an imaginary divided circle of the burner periphery. The burner opening 14 is made, for example, o a ceramic mass, and is built into a tube basket 18 which is formed from the tubes of the wall tubing of the combustion chamber.
The stepped-air nozzles or jets 16 can be embodied either as hole-type nozzles 16, or as slotted nozzles or jets (air jets). The air jets result from rernoval of the tubing of the combustion chamber wall formed of a pipe-web~
pipe configuxation. ~le stepped air flow, ~7hich passes in~
to the combustion chamber ~hrough the conduit 15 with the nozzles or jets 16, is regulated by a flap 17.
Burners with the aforementioned structural features generate Elames which in turn generate a considerable con-centration of NO~ in the flue gases. The reaction mechanisms causing the formation o~ nitrogen oxides in teclmical com-bustion are mostly Icnown. ~* the prcscnt, thc!re are essen-tially two dlfferent fornlation reac~ions as follows:
(1) 'rhe thermic NOX formatioll, which is l>asecl upon oxidation oE molecular nitrogen, ~hich occurs or instance amply in the combustion air. Since the oxidation o molecular nitrogen requires atomic oxygen or aggressive radicals (or instance OEI, 03, etc.), such o~idation is strongly depenclent upon temperature, thus thermic NO~; and ~ 2) the formation of fuel NOX, which occurs by o~i-dation of nitrogen compounds bound in the fuel. During the pyrolysis, nitrogen-carbon and nitro~en-hydrogen radicals (CH, HCN, CH, etc.) form Erom these nitrogen compounds. These radicals oxidize to form NO~ already at ~' ~ ~ ~ 5~ ~
relatively low temperatures in the presence of o~ygen be-cause of their reactivity with molecular oxygen.
A reduction of the thermic N0~-formation is accordingly primarily obtained by lowering the combustion temperature and the retention times at high temperatures. Since with the combustion of fuels with bound nitrogen, however, a large portion of the tot~l N0x-fonmation results from the fuel-N0~-reaction, the a~orementioned measures with such fuels are not suficient for complying with the emi~sion standards existing in certain countries. For this purpose, it is necessary to reduce the nitrogen compounds into molecular nitrogen (N2) still during the pyrolysis in the presence of o~ygen. Tests have shown that these reduction reflctions to mo]ecular nitro-gen occur, for instance, when the fuels are burned ~t below-stoichiometrlc condi~ions, that is, with less oxygen addition or air addition than necessary Eor complete combustLon. To achieve optimtlm resul~s, an ~ir ratio between 0.9 and 0.5 is selectecl for the primary combustion ~one as a function of thc limiting or edge conditions (for instance w~ll tempernture of the combustion chamber). I-lowever, to achieve a complete com-bustion of the carbon-hydrogen compounds of the fuel, the reaction products resulting in the below-stoichiometric primary region must then be afterburned.
Tests have shown that with such a two-step com~ustion, both the fuel-N0~-formation (with simultaneous heat removal from the below-stoichiometric region) as well as the thermic N0~-formation can be considerably reduced. In tests utilizing the two-step combustion, the N0x-emission values were reduced appro~ima~ely up to 70% compared with ~m-stepped combustion.
By tests it was proven that the formation of fuel N0~
could be clearly reduced by operating the burner in the near-stoichiometric or below-stoichiometr~c range. In order to avoid losses through incomplete combustion, and co avoid in-crease of other noxious material emlssions (C0, hydrocarbons, and particles), additional air must be blo~ in above the burners in the combustion chamber during the below-stoichio-metric operation of the burners. The disadvantage o this manner of operation is that in the below-stoichiometrically operatecl lower part oE the combustion chamber sintering and corrosion of the tube wal]s can occur. Accordingly, the operational reliabi]ity o~ the system is in clanger.
It has furtherrnore been detennLnecl tha~ by slo~in~ the mixture betwee~n air ~low and fuel ~]ot~, likcwise considerable reduction o;E N0~-emission can be acllieved. For thi.s purpose, Elow or spray burnors, ~or installco, Mre suitable, ~Lth which both the air stream and thc Euel s~leam arc blown in para]lel into the combustion chamber. To achieve a satisfactory igni-tion, the burner streams must, ho~]ever, support each other, for instance in a corner firing or combustion.
With the arrangement of the burners in a front- or coun-ter-firing or combustion, the mixture of air and fuel can, for example, be slowed thereby that the secondary air surrounding 1~5~
the dust stream is blown-in at substantially the same speed.
In a known burner, the secondary air flow or stream is added separately in two tubes, which are arranged annularly with respect to each other, to permit clischarge of, for example, the inner secondary air stream, with a low speed, directly adjoining the dust stream, and of the outer secondary air stream with higher speed. Disadvantageous with this ar-rangement is that an extension of the flame occurs, which has as a consequence larger combustion chambers, and that with the load-conditioned reduction of the secondary air, the speed of the secondary air is reduced below the dust-air speed, whereby the character and shape of the flame change. The ignition could also be disadvantageous]y influenced thereby.
Furthermore, it is known to undertake a primary combus-tion at below-stoichiometric conditions in an antechamber of the combustion chamber, and to aclmix the air necessary for complete combustion with the combustLo[l gases which leave the antechamber. Thc disadvanta~e oE this arran~,ement exists in the danger o tube wall corroslon oE the antech~mber which is operated below-stoichiometric condition.
It is thereEore an object oE the present invention to develop a burner with which, by influencing the secondary air flow and introducing the same at different locations of the combustion chamber, yet always in association with the burner, the combustion is influenced in such a manner that in a pri-mary zone or partial combustion zone directly adjoining the S~'3 burner outlet there is obtained a stable ignition over the entire load range at below-stc)ichiometric condi tiOTlS ~ and in a secondary zone or afterburning ~one adjoining the pri-mary zone the remainder or balance of the combustion occurs at above-stoichiometric conditions.
This object and other objects and advantages of the present invention will appear more clearly from the follow-in~ specificat.ion in connect.ion with the accompanying draw-:ing, in which:
Figure I is a longitudinal section through a burner ~ccording to the present inventive pr:inc~ple; and I~`igtlre 2 is a view of the burner in the direction of arrow F in l~igure 1.
By one aspect o this invention, a burncr is provided for coml)ust,.ion o.E ~uel which con~nlns nitrogen, sai(i burner cornprLsi.ng: a mnin nir sllppl.y concluit; ~ core-air tube which is Ln colnmutllcat:ion wLth sald main air supply conduit;
an oil atoml~i.n~, ~lance central],y arran~ed in sai.cl core-air tube; a dust tube ~hLch sllrrouncl.s at l~ast a part oE saicl core-air tube; a mantle-lir tubc which surrouncls at least a part of sa,id clust tube and is provided with an air inlet which is in communication with said main air supply conduit, saicl mantle-air tube being connected to and in communication with a burner opening which widens conically toward a com-bustion chamber; an axially shiftable twist blade ring arranged in said air inlet of said mantle-air tube; air ~ tj~ 59 nozzles concentrically arranged around said burner opening, said air nozzles being in communication with said main air supply conduit; and a flap for regulating the air flow through said air nozzles.
In accordance with a further embodiment of the present invention, the air nozzles can be embodied as hole-type nozzles or as air jets (slotted nozzles), whereby, for in-stance, the slot-like openings are produced by removal of the fins or blades between the tubes.
In another embodiment of the present invention, it is further proposed that at least two air nozzles, with a max-imum of six air nozzles, be arranged in a divided or grad-uatecl circle, which may be ]ocated concentrically with respect to the mantle-air tube, the divicled circle diameter being at least 1.5 tlmes, with a maximum o~ 3 times, the diameter of the mantle-air tube.
The advantages obtained with the present inverlLion con-sist in that by aclding to the combustion chamber a part of the secondary air by me~ns of air nozzles located externally of the mantle-air tube of the burner, the combustion pro-cedure of the fuel, which contains nitrogen and passes to the combustion, occurs in such a manner that the N0x-values are reduced to a minimum without thereby endangering the ignition of the burner over the entire load range, without sintering and corrosion resulting on the combustion chamber tubes, and without the combustion being impaired.
~ q3 Referring now to the drawing in detail, the burner com-prises a cen~ral core-air tube 1 which is suitable for re-ceiving an oil atomizing lance 5 for ignition firing or for alternative power combustion for oil. The core-air tube 1 is connected with the main air passage or conduit 4 by the passage or conduit 2 and the flap or valve 3. The dust-air tube 6 is arranged coaxial to the core-air tube 1, and is connected to the dust conduit 8 by the dust distributing chamber 7. The dust-air tube 6 is supplied by a coal-dust tube with the dust-alr mixture for combustion. A mantle-air tube 9 is arranged coaxially around the dust-air tube 6, and is connected by flaps 13 with the main air conduit 4. A
twist-blade ring 10, through which the mantle air 10ws axially, can be shifted ~xially by several spindles 11 and the hand wheel 12. The mantle-air passa~e 9 is connected with the combus~lon chamber by the conical]y ~idening burner chalice or openlng 14. Stepped-nir nozzles or jets 1(~ are supplied with air ~rom the ~in air condui~ 4 by se-veral conduits 15. These stepped-air jets or nozzl~s 16 ~o are uniformly distributed over an imaginary divided circle of the burner periphery. The burner opening 14 is made, for example, o a ceramic mass, and is built into a tube basket 18 which is formed from the tubes of the wall tubing of the combustion chamber.
The stepped-air nozzles or jets 16 can be embodied either as hole-type nozzles 16, or as slotted nozzles or jets (air jets). The air jets result from rernoval of the tubing of the combustion chamber wall formed of a pipe-web~
pipe configuxation. ~le stepped air flow, ~7hich passes in~
to the combustion chamber ~hrough the conduit 15 with the nozzles or jets 16, is regulated by a flap 17.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A burner for combustion of fuel which contains nitrogen, said burner comprising:
a main air supply conduit;
a core-air tube which is in communication with said main air supply conduit;
an oil atomizing lance centrally arranged in said core-air tube;
a dust tube which surrounds at least a part of said core-air tube;
a mantle-air tube which surrounds at least a part of said dust tube and is provided with an air inlet which is in communication with said main air supply conduit, said mantle-air tube being connected to and in communication with a burner opening which widens conically toward a combustion chamber;
an axially shiftable twist blade ring arranged in said air inlet of said mantle-air tube;
air nozzles concentrically arranged around said burner opening, said air nozzles being in communication with said main air supply conduit; and a flap for regulating the air flow through said air nozzles.
a main air supply conduit;
a core-air tube which is in communication with said main air supply conduit;
an oil atomizing lance centrally arranged in said core-air tube;
a dust tube which surrounds at least a part of said core-air tube;
a mantle-air tube which surrounds at least a part of said dust tube and is provided with an air inlet which is in communication with said main air supply conduit, said mantle-air tube being connected to and in communication with a burner opening which widens conically toward a combustion chamber;
an axially shiftable twist blade ring arranged in said air inlet of said mantle-air tube;
air nozzles concentrically arranged around said burner opening, said air nozzles being in communication with said main air supply conduit; and a flap for regulating the air flow through said air nozzles.
2. A burner according to claim 1, in which said air nozzles are hole-type nozzles.
3. A burner according to claim 1, in which said air nozzles are slotted nozzles.
4. A burner according to claim 1, which includes two to six air nozzles arranged in a divided circle having a diameter between 1.5 and 3 times the diameter of said mantle-air tube.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000359729A CA1145659A (en) | 1980-09-04 | 1980-09-04 | Burner |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000359729A CA1145659A (en) | 1980-09-04 | 1980-09-04 | Burner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1145659A true CA1145659A (en) | 1983-05-03 |
Family
ID=4117818
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000359729A Expired CA1145659A (en) | 1980-09-04 | 1980-09-04 | Burner |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1145659A (en) |
-
1980
- 1980-09-04 CA CA000359729A patent/CA1145659A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |