Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
13LIRNERS WITH REDUCE~D POLl~UlT~lNT E~ISSION
Burners which s~uld display reduced emis~ion aF pollut~nt~, especiaily
environment~l~ harm~ul nitro agn o~ide, must b~ ~d~pt~d to a combustion ~echnique
uvhich s~ks to decrease the torm~tion ot su~h pollutarfts.
Nrtr~n oxida is formed d~ring the ~mbus~ion prc:~ss essenti~lly from ~e
molQcular nitr~n present in ai~ and ~rom th~ nitro~,n combin~d in ~ fuel. Them~al
nitro~n oxi~Q ori~in~es in th~ re~ion of ~he flame root or in hot fl~me zon~s a~temp~r~res above 1300'~ ~rom dissoc~d oxyg~n moie~Jles and ni~o~en
mol~les. Formation o~ thermal NOX is dspendent on ~n5:;entration of ~e rnolecular
nit~ogen as w~ll a~ ~a dis~ociated oxy~n ar7d depends stron~ly on temper~u~e.
primary sign~can~e f~r thg ~uel / ~tOx ~ormation i8 th0 oxyg0rl coneentra~on in ths
combu~tion air or the oxidation gas. In both ca~ h~ ~xc~ss air coefficient ~ Is
accordingty a maJor in~u~nce tactor.
5tudi 3s show that the concerltration of nitrogan ris~s with the furnac~ chambertemp~rature as w~ll as exponential~ with the ~ombustion air temper~ture; it ha~ a
t5 maximurn in the close stoi~hiornetric combu~tion ~one (excess air coemcient
approxim~te~ , and ~creases sh~ to ghe su~stoichiom~tric and su~r-
stoichiomstric zone (;~ - 0.6 or ~, ~ 1.6). rhe concentra~n ~ ni~rog~n ~an be low~red
by redr~ulation of ~aste ~ases, wher~by th~: redu~tion in NOX is exponential~y r~latad
to the recy~ed waste gas fl~w (G~s Wàrme ~Gas He;~t] In~ematlonal 38, ~1989~, ~ol.
~0 10, D~mber~
In tho combustion technique the aim is ~ lowsr the oxyç~en ~nd nitfaS~en par~ialpr~ssure and th~ combustion tempera~re in order to r~du~ ~he nitro~en oxide.
Ac~ordin~ly, oxygen-~nrich0d air or pure oxygen is us~ a~ oxi~ation ~as to
minimize the supp~ of nitrogen. Howev~r, the r~s~lt of thi~ is hi~her ~arne
~mperatur~s and a higher oxygen p~ial pressure. ~o redu~e the suppiy of oxygen
US8 iS made of the recydin~ o~ ~urnt out waste gases into tho eornbustion air or the
oxid~tion ~as, effe~iYely reducin~ the oxy~aen c~nten~ by rarefa~ion on ~ ona hand
2 ~73~
and on the other low~ring th~ combustion temperatur~ on the bas~s o~ the waste ~a~
ballast which draws heat frorn th~ flame. This produ~s an ~fficient suppiy of cosled
was~e ~ases to the v~cini~y c~f the flaune root.
Cooling combu~ion charges are also u~ed for low~rin~ ~e ftam~ temperature.
~ucces~ive conlbuæti~n is ~Iso suitable ~or ~he same p~Jrp~se (~ W~rme EGas ~est]
Int~n~tional 39, (1~ , v~l. 6, June). Coolin~ cornbu~ion charges, introduced tQ the
flame, mu~t ~i~play ~ cer~in ~3~ometry, mu~t be produc~d from special mat~riaJ~ and
must b~ pla~d pr~ ly in the burner. Should these co~bustion charg~s not b~
optimally suited to th~ ~rner and the ~bus~ion, the result cc~uld be e;ther irnperfe~t
o~olin~ of th~ flame wRi~out e~ential NOx redu~ion, or exc~ss~v~ lowenng o~ the flame
t~mperature, related tv higll CO emi~ion.
Dovvn~m, that is, in the direc~on of the fl~m~, bum~rs ~r succ~ssive
co~nbustion have drawn supply duc~s for th~ comi~ ion air or ~e oxidation gas whidl
in th~ low~r section near the burner ~low, by way ot pr~mary air openings, ~e supply
of only a mininlal quantity of oxyg~n an~ which in th~ ~pp~r section ~lo~, by way o~
secondary and ter~iary air opsnin~s, the supp~ of a quantity of o~ç~en corr~spon~in~
to close s~oich.oms~ric combustion. Ths flame temperature consequently remains far
below ~hat o~--rring ~uring singl~sta~e combu~tion.
me disadvantaQes of this succe~sive cornb~s$is~n ~ith so-cailed 's~nd~y air
obsta~ realized fo~ ~e combustion alr in the 5~,1pply duet are that thesc ob~taGle~,
which surround the burner in th8 fo~m of ~ mantte, af~ subjec~ed to a ~tron~ hest
eff~ct, sinc~ they are located downstre~m ~f ~he cornbus~ion gas openin~, and that the
forn~ of the man~l~ has ~onsidsrable influenc~ on th~ CO emissi~n which mwst be
speciflsd prior to use ~ ~he bumer anct which rencler~ unusabte many ernbodiments
~n account of excsssiv9 C:O ~mission.
The o~ect of ~r~ prasent inven~ion is consequently to d~velop an ilnproved
~umer which allo~ ptim~l use of the p~sibilities outline~ for red~cin~3 poll~tants and
which avoi~ls the nominat~d ~i~advantages o~ known burner embodiments.
lhis e~ercise is s~lved accordin~ to the present invention by placin3 ~he end
ot each supply du~ f~r the f~ei so th~t i~ proj~ts by a section o~ length L bsyond
the end of ~ach suppty ctuct for the o~ygen or the gas eontaining oxygen.
~73223
The burn~r according to the pr~ser~ invention compr~s~ ~y way of ~xamp~e o~
a central supply duct ~or th~ h~el an~ s~veral s~Jpp~y du~s conc~ntrically surroundin~
~e form~r for ~he ox~ation g~8 Çontaining oxygen. E~y means of the upply duct for
the fuel projectingl 7h~e oxid~tion g~s j0~ Qrnergin~ ~om the indiv~dual r)oz~les can
sllck in wast~ gasas trorn the fumace chamb~r, thus also in~r~ combustion p~oducts,
by means ~ tl~e resuttin~a suction effect of these jets prlor to mixin~ with the fu~ j~.
The longer the pro~scting section of ~e fue~ supply duc~ more ~ubst~nti~l the
reduction of the oxy~en partial pressur~ become~ on aceount o~ ~he inc~der~
r~rff~a~ion.
Th~e jets containin~ ox~n and spteadinç~ downs~ , and whic~ surround
the ~ntral ~1 jet ~or examplc, ensure lonç1 rnix~n~ Icngths which guarar~e sven
intermixing of ~uei and oxidation gas and avoi~ the formation of 't~ot s,ool~', or ho~
flamo zon~s.
i-urthermo~e, th~ flam~ temp~ratu~ can be lowered by aspiration ~f inert
combustion produ~ts and su~stoichiometric combus~on is guarar~ed oVef a large
area, effective~ count~actin~ any formation o~ nitro~n oxide.
tt p~o~s ~dva~lta~eous if th~ 10n~th L o~ the proiecting ~ction of th~ supply
d :~ct for ~e fuel is many tin e~, pre~rab~ at lea~t ei~ ~htfold, ~e diam~ter c~h of the
~upply duct fol the oxygcn or the ~as containin~ oxyg~n.
2~) At a ~onventiona1 d~artc~ of ~h~ supply ducts for th~ oxi~agion ~ om th~
~upply duct for ~he fuel of around one to thre~ time~ the diametar dh of the oxidation
ducts, a sharp~ incid~nt re~u~on o~ emi~ed nitJogen oxide occurs ~t a l~n~th L ~t
ths projs~tinç~ s~ction ~hich amount~ to ~ht times the diame~0r dh. This reduction
in~reases with an increasing iength L.
2~ Here and h~reina~r, th~ so-calied hydraulic diameter of th8 openings o~ the
supply ducts for the oxidation !3as are under~tood as tt e diam~-ter dh. This ~lydraulic
diameter is calcul~ted ~rc)m qu~ruplin3 the cros~;-section~ surface A, divid~ by the
~ircumf~r~n~ U of the supply d~s, thu~ dh = 4,~/U. Accordingty, i~ is taken intoaccc: unt ~hE sl~pp~ du~s. whic:h have no ~irclllar opening cross-section, can also ~e
put to use.
2~73~23
In an advanta~eous variant, ghe end piec~ o~ sach supp~y duct fo~ ~he fu81 iS inthe form ~ a conicaliy widening con~ on its ou~3;de.
This widened en~ piec~ rep~esents a hindranc~ to the oxid.~ltion g~s j4t
oc~urring with consid~rabls impu~, on whi~h a pwtion o~ this je~ is slow~d down. Thi~
5 impulse r~duction and the simul~an~ous Yo~iCity incr~ase ~e quali~y of ths i~termixin~
~f th~ t~el wl~h the o~dation ~s and the stability of the flam0.
The diame~er D at the end of th~ conically wi~necl end piece of each supply
du~t ~vr the fuel ~ pr~fera~ly a~ Iaast 1.3 time~ the int~rn~i di~me~er df~ ~ the supply
du~t for ~he fuel. In the ~se ~ non-clrcu ar cross-section~, the~e diams~ers ar~ to be
understood a~ain as hydr~ullc clian~etsrs.
In or~er to cau~ th~ principl~ of ~uccessive combustlon to r~act ~Yen m~r~
stron~ an ad~fanta~e fur one or morv bors holas to be mad~ through the
conically wid~ned end piece of ~a~;h svpply duct for th~ fuel.
A sm~ll portion ~ the oxidat;on gas ~owin~ past ~e widened encl piece ot the
fuel supply duct is fed through th~se bore hol~ rld then strikes th~ l jet directly
at thQ burner n outh. llle quanti~y of oxy~en passin~ through th~ bore hol~s is
de~flrminbd by the diameter ~ the bore hdes and measured ~3:Jch that sub-
~toichiofnetnc com~ustion occurs ~irect y at thB flams root. The flan e l~ k~pt stable
a~ bumer mouth and burn~ ~hsre with a low flan~e ternperature.
That p~rt of th~ oxida:tion ~as jet dlyened at th~ ~idened snd pie~ finally mixes
w~h t7e residual ~u~l in th~ eme~in~a flame and combust~ this ~ith an exc~ss aircoamcient ~. incr~sin~ down~ream. ll~e maiority oS th~ flame then bu~ns ~s~
stoishio~etrical~ ca. 1.05) with flams ~emperatu~s ~w~r than with sinç3le-staç~
combu6tion.
The burner a~cordin~ to the present inv~ntion enables known ~ro~s~ r
nitfoQen ~xide raduction such as successive ~m~ustion. vlJaste gas r~circulation,
lowe~ing of the combustion ten~pera~ure, even interrnhun~ o~ fu~ and ~xidation ~as by
me~ns of the indicated ~eatur~ to ~ realized simultaneo~ly, and ehus i8 suited
precominantly ~o fum~ee firing whi~ main~ining incr~sed end v~lues for ni~ogen
oxide and ~arbon monoxid~.
~73223
Arl ernb~3dinl0rit shall hereinaft~r descr7be the u5e of the burner according to the
pr~ent invention.
Figure 1 schematic~l~ r~pr~snts th~ ion o~ an ~mbodirnent ~f th~
burner accor~ing to ~e pr~sent invention in a side Yiew;
~i~ur~ 2 show~ a vi~w of ~ burn~r mo~h.
The plan vi~v of Fi~urs 2 shows the contrally disposed ~upply duct 1
fu~t in this exampl~, the fiv~ supply du~s 2 fs~ the oxidation gas disposed
conc~ntricaliy around the f~rmer, and the other five bore holes :3 throu~h ~e widene~
snd pie~e ~1 supply dllct 1. The numb~:3r an~ g~ometric ~orm of all ~upply du~t~ 1 ~d
2 and bore hol~ 3 can b~ alt~r~d according to ~slrecl u~e.
Flgu~s 1 ~hows an emb~diment of tha bum~ ~ccordin~ to ~he prssent invention
with central supply du~t 1 for the natural gas fu~l and supply ducis 2 sutroundin~ thi~
1~ for ths oxidation ~3as, for whic~ o~yçlen i~ usecl. Supply duct 1 proj~cts ov~r the ends
of supply duGts 2 a~cording ~o the pr~sent inver,tion by a section o~ the length L. In
~hi~ case approxin-at@ly ninet~n timss ~e v~lue ~f ~e di~m~or C~h of ~upply duc~3 2
is select~cl aS ~8 Isnçlth L.
Bore hoies 3 ~re fnads through ~he ~nically wi~ening ou~er ~ide of t~ ~nd
pieçe of supply duct 1 for ~he hlelj thus al3o~Ann~ ~ r~s~rided cluantity ~f oxldation g~s
flowing ~rorn supply duc~ 2 to ~ow throu~h. lhs di~m~t~r D at th~ ~nd of the conically
widen~d end pie~ amounts to tN~ and a hal~ tirnes the int~rnal diameter cl~ of ~upply
duct 1.
On ~ way ~o the end piece o~ supply duct 1 th~ o~y~n j~ts eme~ging from
~ ~ 25 supply du~ts 2 ~uck in cool~d ~om~ustion gases origina~ing at the flame ~ncl, and ~u~
provid~ ~r recirculabon of the ~ombustlon produc~s in the furnace. That portion of thi~
~: oxidation g~s flowin~ through bor~ hol0s 3 is mixed at the burn~r mouth with the
natufal gas fuel and thi~ m~u~s csm~usts ther~ xub-stoichiometrically.
The ren~ining portion of th~ ~idaion ~as jet widsning downstrean~ flowing
pa~t the end pleca of SL~ y duct 1 for the fuel is mixed with the partially ~mb~sted
fuel in the fl~me and fin~lly combusts this oomplet~ly. Fur~h~r reduction ~ the flame
2~73~3
ternperature is achleved by the a~pir~ted Inert c~mbustion produc~s which drav~ heat
from the ~ame. At th~ sarne time, the desired su<::c~siv~ combustion for r~ducUon in
NOX emission can be r~alized by thi~ arr~ng~m~n~.
- In ~r~mely high ~mpera~ur~ ndanger th~ thefn~al stabil~ty of the
burner ma~erial, Cot)iing of s~pply dUct 1 fQr th~ fuel can ~ ~fle~
Utilization of th~ bwn~r accordinç~ ~o the p~esent invention produc~s a lon~,
drawn out, soFt y~llow flarne w~h ~ven t~mpe-~ture distributi4n wi~ 'hot 51~ ;'. In
~e end zone the flame burns wnh an ~xoess air coeffici~n~ ~ 1.05. T~e
r~cycled/aspirated ~led combustion pro~ucts an~ the succ~ssiYe combustion
O pro~ide for a low temperaturs at tha ~am~ raot. SlJccassive c~m~ustion ~n ~ carried
out in the burner accordin~ to th~ pres~r~ ~nver~n with much sm~ r lin~ar
dlmension~ than ~as hitherto po~sible. A ~rther advantage is the low-noi~e
~omi~u~tion opera~on.
Waste gas m~surem~nts ~uring operation of the burne~ accordin~ to th~
pr~s~nt inv~ntion at a he~t effici~ncy of 1 MW produce around 1~0 mg ~10,~/Nm~ waste
gas and around 40 m~ C0 w~h ~ furnace chamb~r temperatur~ o~ oa. 1~ and
an oxy~3en conterlt in the was~e ~a~ o~ ca. 5%. ~ early ensures fallinç~ b~w thecorrespon~ TA ~ir end valu~&
