CA2351663A1 - Method for operating a combustion plant - Google Patents

Method for operating a combustion plant Download PDF

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Publication number
CA2351663A1
CA2351663A1 CA002351663A CA2351663A CA2351663A1 CA 2351663 A1 CA2351663 A1 CA 2351663A1 CA 002351663 A CA002351663 A CA 002351663A CA 2351663 A CA2351663 A CA 2351663A CA 2351663 A1 CA2351663 A1 CA 2351663A1
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CA
Canada
Prior art keywords
reducing agent
nitrogen
sub
air
stoichiometric
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
Application number
CA002351663A
Other languages
French (fr)
Inventor
Hermann Bruggendick
Andreas Hospital
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Steag Energy Services GmbH
Original Assignee
Individual
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of CA2351663A1 publication Critical patent/CA2351663A1/en
Abandoned legal-status Critical Current

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23JREMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J7/00Arrangement of devices for supplying chemicals to fire

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Regulation And Control Of Combustion (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
  • Gas Separation By Absorption (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
  • Cylinder Crankcases Of Internal Combustion Engines (AREA)

Abstract

To reduce the quantity of nitrogen oxides resulting from the nitrogen presen t in fuel, a substoichiometric flame zone is generated and a nitrogen oxide reducing agent introduced into said substoichiometric flame zone. When the oxygen supply is discontinued the reducing agent increases the concentration of radicals which in turn reduce the nitrogen being produced and release molecular oxygen.

Description

METHOD FOR OPERATING A COMBUSTION PLANT
The present inverttion relates to a method acxordlng to the introductory portion of claim 1.
Reducing emissions of pollutants when fossil fuels are burned 1s important in terms of environmental protection. Particularly critical are those pollutants that can neither ba filtered out nor washed out.
Among these are nitrogen oxides, primarily N10 end NOa. A
to differentjation should be made . between nitrogen oxides that form thermally, ths~t form based on atmospheric nitrogens, and those nitrogen oxides that r~suit from fuel nitrogen. Thermal nitre~en oxid~s occur largely at temperatures above 14pQ°C. Their occurrence can be controlled in certain . processes by appropriately . controlling the temperature, In contrast, nitrog~n oxides that are based on fuel nitrogen form even at low combustion temperatures:
The SCR method is primarily used by large-scale commercial plants for reducing emissions of nitrogen oxide. SCR stands for Selective Catalytic Reduction. A reducing agent is added and the 2 o spent combustion gas beyond the burnout zone ils conducted through a catalytic reactor in which the nitrogen oxides are split up at temperatures of 30g - 400°C and molecular nitrogen is formed. The capital investment required for the catalytic reactor is substantial. In addition, operating costs are high since the c:atalyzers have to be cleaned and reconditioned, Also known is the SNCR method., SNCR~ stands for Selective Non-Catalytic Reduction. In this method, the reducing a~ont is introduced directly after th~ burnout zones into the super stolchiometric spent combustion gas that is at a higher temp~rature. The same reactions take place, as in the catalytic reactor, but without s cata~rzer at ~r higher temperature and with less of a loss in pressure. A
temperature window must be maintained that is betvve~en 8fi0 and 1050°C. Above this temperature window there is the. risk that the reducing egcnt will oxidize to nitrogen o~~idea in the prosence of the prevailing excess oxygen. Below this temperature window the desired reactions do not occur on a large enough scale. The reducing agent slip, that !s, the reducing ag~nt is carried ;away by the combustion gas as an ineffie~lve Inert, tn addition, the efficiency of the $NCR method requires the reducing agent to be mixed very intensively ~nd uniformly, for Instance with lances and the litre, using a propellant with the spent combustion gas. This ,method Is thus not suitable for large-scale ~ommerciai use. tts application is limited to smaller combustion plants, for Instance to combined heat and power s#ations and garbage incineration plants. Large-sc~ier commercial use would require mixing 2~ via a cros8-seetlon of.100 -- 5Q0 mz to be performed identlcaliy. which is effeCfively impossible.
The difficulties involved with mizlng the reducing agent lntensiveiy and uniformly into the stream of combustion gas also have a negative ~on the high-temperature method currently in z HER of Llte~al Transl off' PCT/E~g9/0804p ~ ~~Ad AG - Az~b73 i!

development. In this case, the reducing agent is introduced into a reduction zone that is situated between the burner zone and the burnout zone. Bumer zone and reduction zone ere operated sub mtoichiometrlcally. It can be necessary toy work with fuel graduation, that is, to add a residual pan of thp fuel to the reduction zone. A terrier medium is n~quired for adding the reducing agent. Air is not suitable since the reduction zone must remain sub-stoichiometric. Nitrogen is expensive. That leaves water vapor and liquids that can be evaporated, wherehy the effciencr of .she ;,,ro:,e~ drops ;~; tr,~,tt-, ~svs.
1o The same holds true for adding ammonia water, whose evaporating water portion is approximately 75°~6, In the burnout zone, which is adjacent to the reduction zone, the air factor becomes greater than 1 due to the addition of additional combustion air.
The portion of resultant NO is comparatively low due to the lack is of oxygen in the reduction zone. When the reducing agent Is added, the NO is split up end molecular nitrogen is ifonned.
In addition to the problems s~ssoclatsrd with mixing the reducing agent uniformly and intensively into th~ reduction zone, there are regulation problems, as well. The burner zone naturally becomes ZQ shorter when there is a change in Toad. The reduction zone must therefore be moved closer to the burners. 1111hen the load is increased, !t is necessary to prevent the reduction zone from migrating into the burnout zone arid coming into contact there with addklonal combustion air, which would bring about super stoichiometric ocnditions.
xPfiR of Literal Transl of PCT/~p99lOSO4o . g~,,a~p pG - Az,2673 A method of the initially mentioned) type is known from WO
91110a3fi4. In this document, the reducing :pent Is introduced Into the primary zone as finely divided materis~i in particle form. Thus, the ditHcuhies described above result relative to the distribution and mixing.
s The reducing agents r»entloned ere calcium sulfide, calcium oxide, iron sutflde and iron oxide as well as mixtures thereof. The reduction ett'ect of these mat~tials Ds at least limited.
The objet of the present invention is to provide a method of the type cited in the foregoing that i$ suitable for large-scale commercial Io employment in a mover efil9clent end more reliable manner with lower capital and operating costs.
For achieving this object, the method cited in the foregoing is inventively provided with the featur~s of the .characterizing portion of claim 1.
The sub-stoichlometrlc flam~ core hiss a comparatively small cross-section, so there is no problem distributing the reducing agent uniformly via this cross-section. . Changes ire load do not affect this, either.
Ammonia is generally selected for the reducing agent; ammonia 2o wet~r, urea, and other nitrogen compounds can also be used, ass well as hydrocarbons, especially natural Bas (Cii~). Practically the entire quantity of available oxygen is used for partially oxidizinD the carbon in the sub-stoichlometric frame zone. Only a errs)) amount of NQ occurs.
The presence of the reducing went ensures that the concentration of HER of Liters) T~s1 of PCT/Epg9/08040 - STBAC3 AG - ,Az2673 the retdlcais NHi, CHI, and HCN increases, These radleais react with the nitrogen monoxide that has occurred, reduce it, and thus permit molecular nitrogen to occur.
Furthermore, the method in accorda~rtce with the invention has s none of the ternpereture timttations that affeot the SNCR method, t7n tho contrary, it has proved to be particularly advantageous to adjust me temperature In the sub~stolchlometric flame zone to over 9 ~ t30'C.
The temperature of the process should preferably be controlled such that upon le~t~er burnout, that ia, when air is added subsequently, io the nitrog~n molecules that have occurred (ag well as the Nz molecules in the combustion air) do not break down thermally and form nitrogen oxides. This means that the termperat~uro should not rise above 94pp°C.
There is no neggtive effect if too much reducing agent is is employed. Thus, no reducing agent slip can occur becauso the reducing agent is completely converted during the subsequent burnout when oxygen fs added. This means that thie residual subatancetc (flue ash and gypsum) can be disposed of with no limitations.
tn a substantial further development of the invention, It is 2o suggested that the sub-stoichiomdtric flarru core be produced as a flame core from fuel and primary air and be ~nveloped with a veil of secondary air, preferably also with anoth~:r veil of tertiary air. The break-down and reduction of the NO take place in the sub-gtoichlometric flame Core. The veils of secondary air, and preferably of s IPER of Literal Traasl of PCTlEp9gI08040 - STEAG AG - Ax.2673 tertiary air; then ensure that the fuel burns out and the excess reducing agent breaks down. The combustion gas thus does not come Into contact with the surrounding wells when in the sub-stoichiometric state.
This effectively prevents the occurrence of high temperature corrosion, s which is another major advantage of the present invent;on.
'T'he nitrogen oxide reducing agent can b~ introduced into the sub-stoichiometric flame core through lateral or central lances.
However, it Is preferably introduced into th6~ sub-stoichiomctric ~s~me core together with the fuel. Furth~rmore, It can be advantageous to ~ o introduce the nitrogen oxide reducing agent. into the sub-stoichlometric flame core together with the prlrnary air. If necessary, the fuel is already mixed with the primary air or a portion of the primary air. Jn this case the mixture comprises fuel, primary air. and r~ucing agent.
Furthermore, It is possible to blow iinto the flame at least a ~s portion of the primary air as core air, whareby this preferably occurs together with the nitrogen oxide reducing agdnt_ The present invention develops ids advantages preferably wherever the fuel has a high nitrogen content. This is the case, for instance, in bituminous coal, tar oil, heavy oil, residusl oil, process gas, zo and the like. Solid fuels are ground prior to combustion. The reducing agent Can be In colic! corm (also ground) or can also be liquk! or gaseous. The method is suitable for all levels of output and works without any additional Ions in pressure.

1PER of Literal Transl oP'PCT/1rP99/08040 - S'~AG AG - Az_2673 The present invention's main area of application is power plant engineering. The burners ace arranged in a plurality of plan~s ono above the other to the side in the boiler wall, wheroby the cross-section of the boiler can be 100 - 500 m~. Air from above is blown in above s the uppermost burner plane. Each burner Is an independent sub-stoichiometric NO reduction system end deUivers super-stoichivmetric combustion gases to the boiler. As can b~ $een, there is no problem with taming individual burner planes on or off tP$R of Lite~csl Tr~tasl of PCTIE~'99/08040 - sTfiAG AG - Az.2673

Claims (6)

claims
1. Method of burning a nitrogen-containing fuel while reducing the emission of nitrogen oxides, whereby a sub-stoichiometrio primary zone is produced and is supplied with a nitrogen oxide reducing agent, characterized in that, the sub-stoichiometric primary zone is embodied as a flame core, and in that nitrogen compounds or hydrocarbons are used as the nitrogen oxide reducing agent.
2. Method in accordance with claim 1, characterized in that the temperature in said sub-stoichiometric flame core is adjusted to greater than 1100°C.
3. Method in accordance with claim 1 or 2, characterized in that said sub-stoichiometric flame core is enveloped with a veil of secondary air, preferably with another veil of tertiary air.
4. Method in accordance with any of claims 1 through 3, characterized In that said nitrogen oxide reducing agent is introduced into said sub-stoichiometric flame core together with the fuel.
5. Method in accordance with any of claims 1 through 4, characterized in that said nitrogen oxide reducing agent is introduced into said sub-stoichiometric flame core together with said primary air.
6. Method in accordance with claim 5, characterized in that core air is blown into said flame and in that said nitrogen oxide reducing agent is introduced into said sub-stoichiometric flame core together with said core air.
CA002351663A 1998-11-18 1999-10-22 Method for operating a combustion plant Abandoned CA2351663A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19853162.1 1998-11-18
DE19853162A DE19853162C2 (en) 1998-11-18 1998-11-18 Process for burning a nitrogenous fuel
PCT/EP1999/008040 WO2000029094A1 (en) 1998-11-18 1999-10-22 Method for operating a combustion plant

Publications (1)

Publication Number Publication Date
CA2351663A1 true CA2351663A1 (en) 2000-05-25

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ID=7888204

Family Applications (1)

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CA002351663A Abandoned CA2351663A1 (en) 1998-11-18 1999-10-22 Method for operating a combustion plant

Country Status (8)

Country Link
EP (1) EP1131150B1 (en)
AT (1) ATE232133T1 (en)
CA (1) CA2351663A1 (en)
DE (2) DE19853162C2 (en)
DK (1) DK1131150T3 (en)
ES (1) ES2192417T3 (en)
PL (1) PL194273B1 (en)
WO (1) WO2000029094A1 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10142804A1 (en) * 2000-10-17 2002-08-08 Bosch Gmbh Robert Emission control system and method for emission control

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4023921A (en) * 1975-11-24 1977-05-17 Electric Power Research Institute Oil burner for NOx emission control
DE3021875C2 (en) * 1980-06-11 1985-04-25 L. & C. Steinmüller GmbH, 5270 Gummersbach Method for applying the selective reduction of nitrogen oxides from flame combustion with the aid of ammonia
DE3331989A1 (en) * 1983-09-05 1985-04-04 L. & C. Steinmüller GmbH, 5270 Gummersbach METHOD FOR REDUCING NO (DOWN ARROW) X (DOWN ARROW) EMISSIONS FROM THE COMBUSTION OF NITROGENOUS FUELS
NL8902963A (en) * 1989-12-01 1991-07-01 Int Flame Research Foundation PROCESS FOR BURNING FUEL OF LOW NOX CONTENT IN THE COMBUSTION GASES USING THROUGH STAGE FUEL SUPPLY AND BURNER.
US5085156A (en) * 1990-01-08 1992-02-04 Transalta Resources Investment Corporation Combustion process

Also Published As

Publication number Publication date
DE19853162A1 (en) 2000-05-31
PL194273B1 (en) 2007-05-31
DE59904247D1 (en) 2003-03-13
EP1131150A1 (en) 2001-09-12
ES2192417T3 (en) 2003-10-01
DE19853162C2 (en) 2003-04-30
DK1131150T3 (en) 2003-06-02
ATE232133T1 (en) 2003-02-15
PL348340A1 (en) 2002-05-20
WO2000029094A1 (en) 2000-05-25
EP1131150B1 (en) 2003-02-05

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