CN101915425A - Method for controlling selective non-catalytic reduction (SNCR) of grate incineration in garbage incineration generating system - Google Patents
Method for controlling selective non-catalytic reduction (SNCR) of grate incineration in garbage incineration generating system Download PDFInfo
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- CN101915425A CN101915425A CN 201010266336 CN201010266336A CN101915425A CN 101915425 A CN101915425 A CN 101915425A CN 201010266336 CN201010266336 CN 201010266336 CN 201010266336 A CN201010266336 A CN 201010266336A CN 101915425 A CN101915425 A CN 101915425A
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- Prior art keywords
- sncr
- control
- reducing agent
- grate
- concentration
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/12—Heat utilisation in combustion or incineration of waste
Abstract
The invention discloses a method for controlling selective non-catalytic reduction (SNCR) of grate incineration in a garbage incineration generating system. The concentration of nitric oxide (NOx) produced by an urban garbage grate incinerator is measured more correctly to control the supply level of a reducing agent in an SNCR system. A furnace wall close to the upper side of a grate is provided with a hole for sampling and the numerical value of the concentration of the NOx above the grate is obtained through a novel rapid analytic unit. The numerical value is used in a calculation program preset in a controller so as to rapidly control the flow rate of a downstream reducing agent injected into a spray gun. The method can be known as feed-forward control and the defect of the lag of a feedback signal in the conventional all-known popular control method is overcome.
Description
Technical field
The present invention is used for the improved simple and easy control system of SNCR (SNCR) system, nitrogen oxide (NOx) emission that the SNCR system uses reducing agent reduction such as ammonia or urea to produce from the incineration of waste boiler.The present invention is applicable to the SNCR system control of grate-type incinerator, more easy " feedforward " control method.By the injection of reducing agent more accurately, reduced the reduction effect and the operating cost of whole system.
Background technology
The burning solid refuse produces a certain amount of nitrogen oxide (NO in incinerator
x).NO
xBe one group of colourless, tasteless but high activity, contain the NO and the NO of different amounts
2The general name of gas.NO
xAmount changes along with fire grate and furnace design to a certain extent, but typically 250 and 350
PPMBetween the change (7%O in the flue gas
2The drying value).
NO
xThe chemical property of formation thing is directly related to the reaction between nitrogen and the oxygen.Burning control device system in the incinerator had typically both comprised primary air (being also referred to as the lower fire grating air), also comprised auxiliary air (be also referred to as upper fire-grating or cross combustion air).Primary air below being positioned at the roasting fire grate the high-tension room supply and be forced through fire grate, subsequently waste bed is carried out drying (separating out water), remove volatile substances (separating out volatile hydrocarbon), and after-flame (the non-effumability hydrocarbon of oxidation).The amount of primary air typically is adjusted to the excess air that refuse is taken fire in the process and minimizes, and makes the after-flame maximization of the carbonaceous material on the waste bed simultaneously.The air scoop of auxiliary air through being positioned at fire grate top injects and is used to provide the turbulent flow of the hydrocarbon of separating out from waste bed is mixed and destroyed.For a typical incinerator, about 60～100% (api requests of 160～200% stoichiometries (ideal)) of level of whole excess airs, wherein, primary air typically accounts for 50～70% of whole air.
Except destroying organic matter, one of purpose of this combustion method is to make NO
xThe formation thing is minimum.NO
xIn combustion process, form: come from the fuel type NO that the elemental nitrogen (N) of the combination of existence in MSW (MSW) stream is carried out oxidation by two main mechanism
x, and come from atmosphere N
2The heating power type NO of high-temperature oxydation
x
Because NO
xEmission is as the role of important pollutant, sour gas and ozone precursors, NO
xEmission to the environment tool with huge destructive power.NO
xDirectly harm concentrates on the influence of these gases to respiratory system.From NO
xThese and other particle that produces enters into the responsive part of lung dearly and can cause or worsen potential mortality breathing problem, such as pulmonary emphysema and bronchitis.
In addition, NO
xEmission also causes other environmental problem.For example, work as NO
xAnd VOC (VOC) is with heat and sunlight one when reacting, formation ground level ozone.Children, asthma patient and work outside or the people that takes exercise is subjected to the adverse effect of ozone easily, these influences comprise that lung tissue destroys and PFT decline.Ozone is vegetation destruction and minimizing crops harvest also.NO
xForm acid with sulfur dioxide with other substance reaction in the air, acid is along with rain, snow, mist or dried particle fall earthward as acid rain.Acid rain destruction or damage car, building and monument also cause lake and river to become and are unsuitable for fish.
In addition, NO
xStill influence the indirect greenhouse gases of atmosphere hydrogen-oxygen (OH) base.Specifically, NO
xThe decomposition of gas causes the OH amount to increase.Multinational government has passed through various laws and regulation limits the NO in incinerator and other sources
xEmission.For example, at 40C.F.R.P
ARTAuthorize in 60
THEU
NITEDS
TATESE
NVIRONMENTALA
GENCY(U.S. environment affairs office) supervision and restriction are from the NO of MWC
xSimilarly, in the world, there is similar restriction NO such as Europe, Canada and Japan
xThe regulation of emission and regulations.
Two kinds of NO are arranged
xControl technology: burning control and after-combustion control.Burning control is by reducing O in the flame in combustion process
2Availability also reduces combustion zone temperature and limits NO
xFormation.These technology comprise the recirculation (FGR) of stage burning, low excess air and flue gas.Stage burning and low excess air reduce the flow of lower fire grating air, with in order to reduce the O in the combustion zone
2Availability has promoted some NO that form like this in main burning
xElectronation.In FGR, a part of burner flue gas is returned to combustion air source, by reducing combustion zone O
2, suppress flame temperature again.
After-combustion control refers to removes the NO that produces in the combustion process in the incinerator
xEmission, the most normally used after-combustion NO
xControl comprises typical a large amount of reductive NO
xSNCR (SNCR) system, perhaps typically even than the more effective reductive NO of SNCR
xSCR (SCR) system.As described in greater detail, SCR system building, operation and maintenance are got up more a lot doubly than SNCR system cost, therefore use for refuse incineration and power generation factory in a lot of places in the world, and be infeasible economically.
SCR a kind ofly promotes NH with catalytic way
3And NO
xBetween the reaction additional control technology.The SCR system can use and contain tax or anhydrous NH
3Reactant, the main distinction are NH
3The size of vapo(u)rization system and the requirement of security.In the SCR system, accurately the reactant of amount is metered in the waste gas stream.Reactant decompose ammonification and on the catalyst that is positioned at the decanting point downstream with NO
xReaction.This reaction is with NO
xBe reduced into nitrogen and steam.The SCR system typically operates in about 500～700 temperature.With regard to waste disposal expense effect and cost efficiency, because high capital cost and catalyst are changed and handled, SCR generally speaking has higher cost.
By contrast, SNCR does not use catalyst with NO
xBe reduced into N
2With the SCR system class seemingly, the SNCR system is injected into one or more reducing agents (perhaps " reactant ") in the combustion furnace, with NO
xReaction also forms N
2Do not have the help of catalyst, these reactions occur in about 1600～1800 temperature.When a small amount of introducing reactant, nearly all reactant has all consumed, and the amount that increases reactant in the SNCR system can cause further NO
xReduction.Yet, when near operation SNCR system SNCR performance range upper end, excess reactant may be added to reative cell, then, excess reactant is by MWC and finally escape in the atmosphere promptly a kind of phenomenon of not expecting that is known as the escaping of ammonia (AMMONIASLIP).
The SNCR system is known, and for example by L
YONBe disclosed in No. 3900554 United States Patent (USP) and by A
RANDDeng the people be disclosed in No. 4208386 and No. 4325924 United States Patent (USP)s in.In brief, these patent disclosures ammonia (L
YON) and urea (A
RANDDeng) can in the actual temp window, be injected into hot combustion gas, with same NO optionally
xReaction also is reduced into two Nitrogen Atom and water with it.Although be described in conjunction with the MWC system here,, SNCR also is used to reduce from the NO that injects coal furnace and other combustion plant such as oil burner and Diesel engine
xEmission.
Typical slow motion (SLOW-ACTING) controller that uses of current SNCR control is based on chimney NO
xEmission is regulated ammonia flow.The amount of the ammonia of in other words, introducing in current slot generally speaking depends on the NO that records in the MWC emission in one or more time section
xAverage magnitude.This method is applicable to such as the NO such as boiler that burn coal or oil firing
xThe process that emission less changes.Even as NO on basis from one minute to another minute
xWhen emission was changed significantly, this known method was also well worked and is satisfied current regulations restrict, because regulations restrict is based on long-term average N O
xLevel such as per day etc., and is set in the level that can realize easily with current control method.If require stricter NO
xRestriction or shorter average period, so, the NO that this usefulness records
xEmission level comes controlling party to answer the known method of thing level just to cause potential minimizing NO
xReduction and higher the escaping of ammonia.
Especially, simply improve ammonia flow to chimney NO
xThe response speed of signal is invalid, because generate NO in combustion furnace
xAnd monitoring that the continuous blow-down thing from the MWC stack effluents monitors delay if having time between the measuring N Ox in (CEM) system.Simply using faster, the control system of response criteria will guide the SNCR system to respond NO by increasing ammonia flow
xEven the temporary transient increase of emission is the high NO that records
xLevel has been left furnace area with the SNCR system.When at subsequently low NO
xWhen level applied extra reactant in the period, the ammonia flow of increase may be excessive, caused the escaping of ammonia to increase.Similarly, SNCR responds NO by reducing reactant flow
xThe temporary transient minimizing of stack effluents, and the reactant flow level reduces the relative higher NO of the processing that may be not enough to the best
xFurnace levels.Briefly, for the process of change not too, perhaps when on the time period of growing relatively, controlling to the restriction of easy realization, the NO in past
xLevel is current NO
xThe good index of level.When at NO
xWhen controlling to stricter restriction in the process of emission height change, the NO in past
xLevel is current NO no longer just
xThe good index of level.
Similarly, current levels of reagent may depend on other measurement result.For example, in the known SNCR of another kind system control, the CEM system measures ammonia slip is with the amount of the unreacted reactant determining to contain in the stack effluents.Change the reaction volume that is applied in the SNCR system with detected current ammonia slip levels then.Yet, ammonia slip levels itself may with NO
xLevel is less relevant, and therefore, conditioned reaction thing level may provide relatively poor NO to minimize the escaping of ammonia
xReducing property.In addition, the escaping of ammonia standard of control SNCR system is for based on NO
xControl system similar defective is arranged, the current ammonia slip levels that promptly records in the emission itself, to about handling final NO in current needed reactant flow of furnace conditions in future and the combustion furnace
xLevel provides limited guidance.
Summary of the invention
The present invention provides a kind of more simple and easy direct control system and method for solving the technical problem that exists in the known technology, but be only applicable at present in the grate-type incinerator, can estimate, in other combustion systems such as fluidized bed incinerator, also can find similar control method.Measure current combustion furnace NO accurately by short-term
xThe data of level, the reducing agent in the SNCR system of control incinerator injects traffic level.This new method is used the ammonia flow of response fast, at high NO
xPeriod increases ammonia, and at low NO
xPeriod reduces ammonia, and this has eliminated intrinsic delay in traditional NOx discharge measuring device.As a result, at NO
xWhen product uprises, increase ammonia flow, then, at corresponding NO
xDuring the product step-down, reduce ammonia flow, therefore, improved NO
xReduction and reduced the escaping of ammonia by excessive the applying that minimizes reducing agent.
Certainly, traditional NO
xThe discharge measuring device remains requisite.It also is that environmental protection mechanism of government monitoring pollutant is necessary.For some concrete cases, control method of the present invention also needs to obtain the correction foundation of the continuous online monitoring data of flue gas.Combustion control system is connected to the SNCR system to provide feed-forward signal can further strengthen the SNCR control procedure to SNCR control.This connection will allow reactant flow reckoning with higher NO
xLevel is to increase and reckoning with lower NO
xReduce during level.
The specific embodiment
The present invention is a kind of NO that is used to control
xThe method of the amount of reducing agent, described method comprises the steps:
By continuous monitoring fire grate top nitrogen oxide (NO
x) concentration numerical value directly controls the injection rate of reducing agent.Sidewall above fire grate is opened and is got sample point, in the sampling period of every 5-6 second, obtains current nitrogen oxide (NOx) concentration value after using ten groups of data weighted averages that record recently.According to above-mentioned (NO
x) the concentration value calculates and be used to control NO
xThe amount of reducing agent, wherein, on the reaction temperature window of reducing agent decanting point in about 50 seconds to the 120 seconds scopes in sample point downstream.
Said method comprises the steps: that further the sampled data circulation of nearest time replaces the sampled data of time farthest, obtains current nitrogen oxide (NO after the weighted average
x) the concentration value.Thereby realize dynamic control NO
xThe implantation concentration of reducing agent.NO
xThe variation of the injection rate of reducing agent is to rely on the concentration of regulating reducing agent when injecting spray gun to realize.
Said system further comprises flue gas on-line monitoring (CEMS) system that is positioned at exhanst gas outlet, and the data that this CEMS system provides only are used for the initial parameter of revised version control system, not real-time participation control.
Although above the preferred embodiments of the present invention are described; but the present invention is not limited to the above-mentioned specific embodiment; the above-mentioned specific embodiment only is schematic; be not restrictive; those of ordinary skill in the art is under enlightenment of the present invention; not breaking away under the scope situation that aim of the present invention and claim protect, can also make a lot of forms, these all belong within protection scope of the present invention.
Claims (4)
1. one kind is used for the control method that waste incineration and generating electricity system fire grate burns SNCR, it is characterized in that, described method comprises the steps: to measure fire grate top nitrogen oxide (NO
x) concentration numerical value; In the sampling period of every 5-6 second, obtain current nitrogen oxide (NO after using ten groups of data weighted averages that record recently
x) the concentration value; According to above-mentioned (NO
x) the concentration value calculates and be used to control NO
xThe method of the amount of reducing agent, wherein, on the reaction temperature window of reducing agent decanting point in about 50 seconds to the 120 seconds scopes in sample point downstream.
2. the control method that is used for the fire grate burning SNCR of waste incineration and generating electricity system according to claim 1, it is characterized in that, said method comprises the steps: that further the sampled data circulation of nearest time replaces the sampled data of time farthest, obtains current nitrogen oxide (NO after the weighted average
x) the concentration value.Thereby realize dynamic control NO
xThe implantation concentration of reducing agent.
3. NO according to claim 2
xThe variation of the injection rate of reducing agent is characterized in that, is to rely on the concentration of regulating reducing agent when injecting spray gun to realize.
4. the control method that is used for the fire grate burning SNCR of waste incineration and generating electricity system according to claim 1, it is characterized in that, system further comprises flue gas on-line monitoring (CEMS) system that is positioned at exhanst gas outlet, the data that this CEMS system provides only are used for the initial parameter of revised version control system, not real-time participation control.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201010266336 CN101915425A (en) | 2010-08-30 | 2010-08-30 | Method for controlling selective non-catalytic reduction (SNCR) of grate incineration in garbage incineration generating system |
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| CN 201010266336 CN101915425A (en) | 2010-08-30 | 2010-08-30 | Method for controlling selective non-catalytic reduction (SNCR) of grate incineration in garbage incineration generating system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103702743A (en) * | 2011-04-27 | 2014-04-02 | 西门子公司 | Method for reducing the emission of nitrogen oxides in the exhaust gas of a furnace during the thermal treatment of materials and furnace operated according to said method |
-
2010
- 2010-08-30 CN CN 201010266336 patent/CN101915425A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103702743A (en) * | 2011-04-27 | 2014-04-02 | 西门子公司 | Method for reducing the emission of nitrogen oxides in the exhaust gas of a furnace during the thermal treatment of materials and furnace operated according to said method |
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Application publication date: 20101215 |