CA2232721A1 - Method and apparatus for controlling the amount of a treatment medium introduced in order to reduce the nitrogen oxide content of the exhaust gases from combustion processes - Google Patents
Method and apparatus for controlling the amount of a treatment medium introduced in order to reduce the nitrogen oxide content of the exhaust gases from combustion processes Download PDFInfo
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- CA2232721A1 CA2232721A1 CA002232721A CA2232721A CA2232721A1 CA 2232721 A1 CA2232721 A1 CA 2232721A1 CA 002232721 A CA002232721 A CA 002232721A CA 2232721 A CA2232721 A CA 2232721A CA 2232721 A1 CA2232721 A1 CA 2232721A1
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- nitrogen oxide
- oxide content
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- exhaust gases
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D11/00—Control of flow ratio
- G05D11/02—Controlling ratio of two or more flows of fluid or fluent material
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
- F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
- F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
- F01N3/025—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
- F01N3/0253—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D21/00—Control of chemical or physico-chemical variables, e.g. pH value
- G05D21/02—Control of chemical or physico-chemical variables, e.g. pH value characterised by the use of electric means
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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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
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- Environmental & Geological Engineering (AREA)
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- Automation & Control Theory (AREA)
- Analytical Chemistry (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Health & Medical Sciences (AREA)
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- Combustion & Propulsion (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treating Waste Gases (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Regulation And Control Of Combustion (AREA)
- Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
Abstract
Method for controlling the amount of a treatment medium introduced into a firing apparatus in order to reduce the nitrogen oxide content of exhaust gases from combustion processes. A mean nitrogen oxide content is calculated, and a first control variable is calculated as a function of the nitrogen oxide content for controlling the amount of treatment medium introduced. A second control variable is calculated as a function of the handling medium slip for controlling the amount of treatment medium introduced. Then, either the first control variable or the second control variable is used as the control variable for controlling the amount of treatment medium introduced.
Description
METHOD AND APPARATUS FOR CONTROLLlNG THE .~IOUNT OF A
TREATMENT MEDIUM INTRODUCED IN ORDER TO REDUCE THE
NITROGEN CONTENT OF THE EXHAUST GASES FRO~I COMBUSTION
PROCESSES
BACKGROUNO OF THE I~lVENTION
l . Field of the Invention The invention relates to a method for controlling the arnount of a treatment medium introduced in order to reduce the nitro~en oxide content of theexhaust gases from combustion processes. The invention furthermore relates to ~napparatus for controllin_ the amount of a h~n(lling mediurn introduced.
'. Description of the Related Art In the case ot' the treatment of e~chaust gases from combuslion processes in order to reduce the nitrogen oxide content. either ammonia is supplied to the e~haust gas flo-v upstream of a reduction catal,vtic converler (SCR process) or ammonia and/or a material which forms ammonia or ammoniurn compounds under the influence of temperature (for example urea, urea sall or similar materials) is injected into the e~haust gas ~low in a secondary combustion chamber (SNCR process). In both cases. ammonia that has not been consumed in the reduction reaction of the nitrogen 2 o oxide is emitted as so-called ammonia slip in the e ~haust _ ses~ which leads to atmospheric contammation.
EP 0 549 904 discloses a method for controlling the amoum of a treatment mediurn introduced in order to reduce the nitrogen oxide content of e ~h~ust gases from combustion processes, which method ~eeps not onlv the nitrogen oxide 2 5 content but also the content of unconsumed ammonia as low as possible. This method has the disadvantage that the aim is to produce as little arnmonia slip as possible. ~nd an increased nitrogen oxide content in the e~haust gas flow must in this case beaccepted. It is particularlv disadvantageous because legallv specified limits for nitrogen oxide ernissions mav be exceeded in this case.
TREATMENT MEDIUM INTRODUCED IN ORDER TO REDUCE THE
NITROGEN CONTENT OF THE EXHAUST GASES FRO~I COMBUSTION
PROCESSES
BACKGROUNO OF THE I~lVENTION
l . Field of the Invention The invention relates to a method for controlling the arnount of a treatment medium introduced in order to reduce the nitro~en oxide content of theexhaust gases from combustion processes. The invention furthermore relates to ~napparatus for controllin_ the amount of a h~n(lling mediurn introduced.
'. Description of the Related Art In the case ot' the treatment of e~chaust gases from combuslion processes in order to reduce the nitrogen oxide content. either ammonia is supplied to the e~haust gas flo-v upstream of a reduction catal,vtic converler (SCR process) or ammonia and/or a material which forms ammonia or ammoniurn compounds under the influence of temperature (for example urea, urea sall or similar materials) is injected into the e~haust gas ~low in a secondary combustion chamber (SNCR process). In both cases. ammonia that has not been consumed in the reduction reaction of the nitrogen 2 o oxide is emitted as so-called ammonia slip in the e ~haust _ ses~ which leads to atmospheric contammation.
EP 0 549 904 discloses a method for controlling the amoum of a treatment mediurn introduced in order to reduce the nitrogen oxide content of e ~h~ust gases from combustion processes, which method ~eeps not onlv the nitrogen oxide 2 5 content but also the content of unconsumed ammonia as low as possible. This method has the disadvantage that the aim is to produce as little arnmonia slip as possible. ~nd an increased nitrogen oxide content in the e~haust gas flow must in this case beaccepted. It is particularlv disadvantageous because legallv specified limits for nitrogen oxide ernissions mav be exceeded in this case.
3 0 The object of the present invention is Ihus to propose a method for controlling the amount of a treatment medium, for example ammonia, introduced inorder to reduce the nitrogen oxide content of exhaust gases from combustion processes, which method has improved characteristics. particularly with respect to compliance with limits.
SUMMARY (~F THE INVENTION
The object is achieved by a method for controlling the arnount of a treatment medium~ in particular ammonia. introduced in order to reduce the nitrogen oxide content of the exhaust gases from combustion processes, in which method a mean nitrogen oxide content and a first controlled variable for the amount introduced lo are generated as a function of the nitrogen oxide content. in which method a second controlled variable for the amounl introduced is generated as a function of the treatment medium slip~ and in which either only the first controlled variable or else the second controlled v ariable is taken into account. as a function of the mean nitrogen oxide content.
In order to complv. in particular~ with legally specified limits~ the nitrogen oxide content of the cleaned combustion gas is measured continuously, ame, n nitrogen oxide content being in particular~ recalculated periodically, for example over half an hour or over '4 hours in each case~ in accordance with the specified limits.
In addition to the nitrogen o~ide content~ the treatment medium slip is 2 o also measured and~ from this (depending on the requirement) a mean value iscalculated~ for example a value a- eraged over a time period of 24 hours The control apparatus according to the invention essentially has two different operating modes. During a first operating mode~ in which there is no risk of an emission limit being exceeded. a first controlled variable for the amount of 2 5 ammonia introduced is calculated as a function of the me~sured nitrogen oxide content, using a nitrogen oxide regulator~ ~nd a second controlled ~ ariable for the amount of arnmonia introduced is calculated as a function of the measured arnmonia slip~ using a slip regulator. A minimum value selection apparatus~ which is connected downstrearn of the t vo regulators. is used to choose the smaller of the two values of the first 3 o controlled variable and of the second controlled variable in order to control the amount of ammonia introduced, which results in reduced arnmonia consumption and less ammonia slip. The control apparatus changes to a second operating mode as soon as there is any risk of non-compliance with specified limits. in particular with respect to nitrogen oxide emission. The mean nitrogen oxide content continuously is measured and compared with a specified limit. As soon as and as long as the mean nitrogen oxide content exceeds the limit, the control apparatus is operated in the second operating mode. this limit which causes the changeover ad- antageously being below the legallv specified emission limit in order in this ~vay to m~int~in a safety margin. In this second operating mode. only the first controlled variable. produced by the nitrogen oxide 0 regulator. is used to control the amount of ammonia introduced, in order to keep the nitrogen oxide content in the pure gas as low as possible.
One advanta_e of the method as claimed in the invention is the ~act that. in a first operating mode. both the nitrogen oxide content and the unconsurned amrnonia content (ammonia slip) o~'the e~haust _ases from the combustion charnber are kept low and that. during a time period when the nitrogen oxide emission is high, a second operatin~ mode is entered. during which only the nitrogen oxide content is kept as low as possible. in order to comply with specified limits, in particular with respect to nitrogen oxide emission.
BRIEF DESCRIPTION OF THE DRAWrNGS
2 0 nle in- ention will be described in detail ~,vith reference to a number of exemplary embodiments. In the t;gures:
Fig. l shows a schematic illustration of a combustion process:
Fig. 2 shows a first e~emplar-~ embodiment of a control apparatus:
Fig. ~ shows a second e:~emplarv embodiment of a control apparatus:
2 5 Fig. ~a shows a slip re~Julator in a first operating mode;
Fig. ~b shows a slip regulator in a second operating mode.
DESCRIPTION OF THE PREFERRED EMBOl~IMENTS
The combustion apparatus l illustrated in Figure l has a firing apparatus 2 which is supplied on the one hand ~ ia a supply line with luel 7 and on the other hand 3 o via a further suppl~l~ line ~~ith a treatment medium 8a the ~low rate in particular of the tre~tm~nt medium 8a being controllable v ia a control fitting 8 and a control apparatus 30, which is illustrated in ~igures 2 and 3. In the illustrated exemplary embodiment, ammonia is used as the treatment medium 8a. The combustion gases 5a produced in the firing apparatus 2 pass into the boiler 3, leave said boiler 3 as untreated gas 5b and, after flowing through the flue _as cleaning apparatus ~ pass as clean gas Sc into the chimney 6, where they are emitted into the atmosphere. A measurement apparatus 9 for measuring ammonia is coupled via a connecting line 9a to the untreated gas 5b flowing through, the measured treatment mediurn slip (ammonia slip) 9b being supplied as an electrical signal to a downstream control apparatus 30. A measurement apparatus 10 for nitrogen oxide may likewise be coupled via a connecting line 1 Oa to the untreated gas 5b flowing through, it likewise being possible to supplv the measured nitrogen oxide content l Ob of the untreated gas as an electrical si_nal to the downstream control apparatus 30. The nitrogen o~ide content of the pure gas Sc is measured by means of a further measurement apparatus 1 1 for nitrogen oxides. via a connecting line 1 1 a. This measured nitrogen oxide content I lb is supplied as an electrical signal to the do~nstream control apparatus 30.
Fig. 2 shows a first exemplarv embodiment of a control apparatus 30. The measured nitrogen oxide content 1 1 b of the pure (treated) gas is supplied to a nitrogen oxide regulator 14 which. taking accoun~ of a predetermined nominal nitrogen oxide 2 o content value 1 1 c. produces a controlled variable 1 1b which is supplied both to a slip regulator 13 and to a minimum value selection apparatus 12. As a function of thenitrogen oxide value measured in the pure gas ~c. the nitro_en oxide regulator produces a controlled variable 14b for Ihe metering of arnmonia water for removing nitro~en from the flue gas.
2 5 The measured ammonia slip 9b in the untreated gas ~b is supplied to a slip regulator 13 which. taking account of a nominal arnmonia slip value 9c. produces a second controlled variable I ~b for the metering of arnmonia water for removing nitrogen from the flue gas. the second controlled variable 13b likewise being supplied to the minimum value selection apparatus 12. The controlled variable 1 3b produced bv 3 o the slip regulator 13 reduces the metering of ammonia water when the ammonia slip, measured in the untreated gas flow ~b from which nitrogen has been removed, exceeds a predetermined nominal value. The second controlled variable 1 3b thus results in a smaller amount of ammonia water being added as the measured ammonia slip 9b rises.
The two controlled variables 13b and 14b are compared with one another s in the minimum value selection apparatus 12, and the smaller of the two values is supplied as the controlled variable 12b to the downstrearn flow regulator 17. This flow regulator 17 is used to ensure that the arnmonia water flow rate, which is pre-determined by the controlled variable 1 2b and is specified as a nominal value to the flow regulator 17, is also delivered. this being achieved in that the ammonia flow rate 0 is measured using a sensor (which is not illustrated) and is supplied as an actu~l value 12c to the ~low regulator 17 which. v ia Ihe controlled variable 1 7a, drives the control fitting 8~ for example a metering apparatus 8 comprisin_ for instance a metering pump, in such a manner that the amount of arnmonia 8a predetermined by the controlled variable 12b is supplied to the tiring apparatus 2.
The control apparatus 30 according to Fig. 2 also has an averaging apparatus 16 which forms a mean value with respect to time from the measured nitrogen oxide content and supplies this mean value as the mean nitrogen oxide content 1 6b, forming the difference from Ihe nominal nitrogen oxide content mean value 1 6c ~vhich is specified using an input apparatus 16d. as a regulated variable 16e to a 2 0 comparator l S. The mean ~ alue is calculated continuously in the averaging apparatus 16 by calculating, for exarnple. half-hourly mean values or daily mean values. If the mean nitrogen oxide content 1 6b exceeds the nominal nitrogen oxide content meanvalue 1 6c, then the comparator 15 produces a logic control signal " 1", which is supplied as the controlled v ariable 1 5b to the slip regulator 13 . If the mean nitrogen 2 5 oxide content 1 6b is less than the nominal nitrogen oxide content mean value 1 6c, then the comparator l S produces a logic control signal "O". Figures 4a and 4b show the slip regulator 13 in the two different operating modes. In the first operating mode~
according to Fig. 4a. the controlled variable 1 5b is a logic " 1 " and the changeover apparatus 19 is in the position shown. ]n the second operating mode. according to 3 o Fig. 4b, the controlled variable I 5b is a lo~ic "0"~ and the changeover apparatus is in the correspondingly shown position. If the mean nitrogen oxide content 16b exceeds the nominal nitrogen oxide content mean value 16c, then the comparator switches to the logic control signal " I " and the slip regulator 13 changes to the first operating mode, as shown in Fig. 4a. In the first operating mode, the controlled variable 13b 5 ernitted by the slip regulator 13 is always identical to the controlled variable 14b of the nitrogen oxide regulator since the proportional path is used in the proportional/integral part 20. so that the output value v is equal to the input value z, w hile the integrator is switched off. This circuit ensures that the controlled value 13b of the slip regulator 13 is always identical to the controlled variable 14b of the nitrogen oxide regulator 14, 0 irrespective of the value x, which is formed from the difference between the nominal treatment medium slip value 9c and the treatment medium slip 9b. In the first operating mode, the controlled variable 13b follows the controlled variable 14b directly and, if necessary, makes a jump when the changeover apparatus 19 s~hitches. The minimum value selection apparatus 12 arranged downstream tries to select the smaller of the two 5 controlled variables 13b, 14b. Since these two values are of equal magnitude in the first operating mode. this ensures that the controlled variable 12b corresponds to thecontrolled variable 14b ofthe nitrogen o~ide regulator 14. Thus~ the supply of ammonia water is now regulated by the nitrogen oxide regulator 14, irrespective of the slip that occurs. so that the control system tries to comply with the required nitrogen 2 0 oxide emission limit~ at the e~cpense of the ammonia slip.
The second operating mode is also designed in particular such that there is no jump in the controlled variable 13b when the changeover apparatus 19 ~switches from z to x. that is to say when it changes over in such a manner that the switch to z is opened and the switch to x is closed. In the second operating mode, an integral 2 5 regulator is connected in the proportional/integral part 20. while a proportional regulator is connected in the proportional part 21, resulting in a so-called PI regulator over311 in the slip regulator 13 in the second operating mode. In this second operatin_ mode~ the slip regulator 13 tries to reduce the difference between the treatment medium slip 9b and the nominal treatment medium slip value 9c to zero. bv producing a 3 o correspondin controlled variable l 3b. In the second operating mode~ the controlled variables 13b and 14b may assume differem values. the minimurn value selection apparatus 12 selecting the smaller of the two values and pre~let~rmining this as the controlled variable 12b for the flow regulator 17.
The second exemplary embodiment of a control apparatus 30~ ~vhich is 5 illustrated in Figure 3, differs from the e.Yemplary embodiment according to Figure 2 in that the nitrogen oxide content is controlled bv means of a cascade control system in that an untreated gas nitrogen oxide content 1 Ob, ~vhich has a more dynarnic response.
is supplied to a subordinate nitrogen oxide regulator 14, and the more inert signal of the pure gas nitrogen oxide content 1 lb is supplied to the superior nitrogen oxide regulator 0 18, this nitrogen oxide regulator 18 producing a controlled variable 1 8b which, with the difference being formed between it and a nominal untreated gas nitrogen oxide content value specified in an input apparatus l Od. producing a preset value for the nitrogen oxide regulator 14. Such a cascade control system has the advantage of better dynamic control response. With the exception of this cascade control system, the hvo control 15 apparatuses 30 according to Fig. 3 and F'ig. ~ are of identical design.
SUMMARY (~F THE INVENTION
The object is achieved by a method for controlling the arnount of a treatment medium~ in particular ammonia. introduced in order to reduce the nitrogen oxide content of the exhaust gases from combustion processes, in which method a mean nitrogen oxide content and a first controlled variable for the amount introduced lo are generated as a function of the nitrogen oxide content. in which method a second controlled variable for the amounl introduced is generated as a function of the treatment medium slip~ and in which either only the first controlled variable or else the second controlled v ariable is taken into account. as a function of the mean nitrogen oxide content.
In order to complv. in particular~ with legally specified limits~ the nitrogen oxide content of the cleaned combustion gas is measured continuously, ame, n nitrogen oxide content being in particular~ recalculated periodically, for example over half an hour or over '4 hours in each case~ in accordance with the specified limits.
In addition to the nitrogen o~ide content~ the treatment medium slip is 2 o also measured and~ from this (depending on the requirement) a mean value iscalculated~ for example a value a- eraged over a time period of 24 hours The control apparatus according to the invention essentially has two different operating modes. During a first operating mode~ in which there is no risk of an emission limit being exceeded. a first controlled variable for the amount of 2 5 ammonia introduced is calculated as a function of the me~sured nitrogen oxide content, using a nitrogen oxide regulator~ ~nd a second controlled ~ ariable for the amount of arnmonia introduced is calculated as a function of the measured arnmonia slip~ using a slip regulator. A minimum value selection apparatus~ which is connected downstrearn of the t vo regulators. is used to choose the smaller of the two values of the first 3 o controlled variable and of the second controlled variable in order to control the amount of ammonia introduced, which results in reduced arnmonia consumption and less ammonia slip. The control apparatus changes to a second operating mode as soon as there is any risk of non-compliance with specified limits. in particular with respect to nitrogen oxide emission. The mean nitrogen oxide content continuously is measured and compared with a specified limit. As soon as and as long as the mean nitrogen oxide content exceeds the limit, the control apparatus is operated in the second operating mode. this limit which causes the changeover ad- antageously being below the legallv specified emission limit in order in this ~vay to m~int~in a safety margin. In this second operating mode. only the first controlled variable. produced by the nitrogen oxide 0 regulator. is used to control the amount of ammonia introduced, in order to keep the nitrogen oxide content in the pure gas as low as possible.
One advanta_e of the method as claimed in the invention is the ~act that. in a first operating mode. both the nitrogen oxide content and the unconsurned amrnonia content (ammonia slip) o~'the e~haust _ases from the combustion charnber are kept low and that. during a time period when the nitrogen oxide emission is high, a second operatin~ mode is entered. during which only the nitrogen oxide content is kept as low as possible. in order to comply with specified limits, in particular with respect to nitrogen oxide emission.
BRIEF DESCRIPTION OF THE DRAWrNGS
2 0 nle in- ention will be described in detail ~,vith reference to a number of exemplary embodiments. In the t;gures:
Fig. l shows a schematic illustration of a combustion process:
Fig. 2 shows a first e~emplar-~ embodiment of a control apparatus:
Fig. ~ shows a second e:~emplarv embodiment of a control apparatus:
2 5 Fig. ~a shows a slip re~Julator in a first operating mode;
Fig. ~b shows a slip regulator in a second operating mode.
DESCRIPTION OF THE PREFERRED EMBOl~IMENTS
The combustion apparatus l illustrated in Figure l has a firing apparatus 2 which is supplied on the one hand ~ ia a supply line with luel 7 and on the other hand 3 o via a further suppl~l~ line ~~ith a treatment medium 8a the ~low rate in particular of the tre~tm~nt medium 8a being controllable v ia a control fitting 8 and a control apparatus 30, which is illustrated in ~igures 2 and 3. In the illustrated exemplary embodiment, ammonia is used as the treatment medium 8a. The combustion gases 5a produced in the firing apparatus 2 pass into the boiler 3, leave said boiler 3 as untreated gas 5b and, after flowing through the flue _as cleaning apparatus ~ pass as clean gas Sc into the chimney 6, where they are emitted into the atmosphere. A measurement apparatus 9 for measuring ammonia is coupled via a connecting line 9a to the untreated gas 5b flowing through, the measured treatment mediurn slip (ammonia slip) 9b being supplied as an electrical signal to a downstream control apparatus 30. A measurement apparatus 10 for nitrogen oxide may likewise be coupled via a connecting line 1 Oa to the untreated gas 5b flowing through, it likewise being possible to supplv the measured nitrogen oxide content l Ob of the untreated gas as an electrical si_nal to the downstream control apparatus 30. The nitrogen o~ide content of the pure gas Sc is measured by means of a further measurement apparatus 1 1 for nitrogen oxides. via a connecting line 1 1 a. This measured nitrogen oxide content I lb is supplied as an electrical signal to the do~nstream control apparatus 30.
Fig. 2 shows a first exemplarv embodiment of a control apparatus 30. The measured nitrogen oxide content 1 1 b of the pure (treated) gas is supplied to a nitrogen oxide regulator 14 which. taking accoun~ of a predetermined nominal nitrogen oxide 2 o content value 1 1 c. produces a controlled variable 1 1b which is supplied both to a slip regulator 13 and to a minimum value selection apparatus 12. As a function of thenitrogen oxide value measured in the pure gas ~c. the nitro_en oxide regulator produces a controlled variable 14b for Ihe metering of arnmonia water for removing nitro~en from the flue gas.
2 5 The measured ammonia slip 9b in the untreated gas ~b is supplied to a slip regulator 13 which. taking account of a nominal arnmonia slip value 9c. produces a second controlled variable I ~b for the metering of arnmonia water for removing nitrogen from the flue gas. the second controlled variable 13b likewise being supplied to the minimum value selection apparatus 12. The controlled variable 1 3b produced bv 3 o the slip regulator 13 reduces the metering of ammonia water when the ammonia slip, measured in the untreated gas flow ~b from which nitrogen has been removed, exceeds a predetermined nominal value. The second controlled variable 1 3b thus results in a smaller amount of ammonia water being added as the measured ammonia slip 9b rises.
The two controlled variables 13b and 14b are compared with one another s in the minimum value selection apparatus 12, and the smaller of the two values is supplied as the controlled variable 12b to the downstrearn flow regulator 17. This flow regulator 17 is used to ensure that the arnmonia water flow rate, which is pre-determined by the controlled variable 1 2b and is specified as a nominal value to the flow regulator 17, is also delivered. this being achieved in that the ammonia flow rate 0 is measured using a sensor (which is not illustrated) and is supplied as an actu~l value 12c to the ~low regulator 17 which. v ia Ihe controlled variable 1 7a, drives the control fitting 8~ for example a metering apparatus 8 comprisin_ for instance a metering pump, in such a manner that the amount of arnmonia 8a predetermined by the controlled variable 12b is supplied to the tiring apparatus 2.
The control apparatus 30 according to Fig. 2 also has an averaging apparatus 16 which forms a mean value with respect to time from the measured nitrogen oxide content and supplies this mean value as the mean nitrogen oxide content 1 6b, forming the difference from Ihe nominal nitrogen oxide content mean value 1 6c ~vhich is specified using an input apparatus 16d. as a regulated variable 16e to a 2 0 comparator l S. The mean ~ alue is calculated continuously in the averaging apparatus 16 by calculating, for exarnple. half-hourly mean values or daily mean values. If the mean nitrogen oxide content 1 6b exceeds the nominal nitrogen oxide content meanvalue 1 6c, then the comparator 15 produces a logic control signal " 1", which is supplied as the controlled v ariable 1 5b to the slip regulator 13 . If the mean nitrogen 2 5 oxide content 1 6b is less than the nominal nitrogen oxide content mean value 1 6c, then the comparator l S produces a logic control signal "O". Figures 4a and 4b show the slip regulator 13 in the two different operating modes. In the first operating mode~
according to Fig. 4a. the controlled variable 1 5b is a logic " 1 " and the changeover apparatus 19 is in the position shown. ]n the second operating mode. according to 3 o Fig. 4b, the controlled variable I 5b is a lo~ic "0"~ and the changeover apparatus is in the correspondingly shown position. If the mean nitrogen oxide content 16b exceeds the nominal nitrogen oxide content mean value 16c, then the comparator switches to the logic control signal " I " and the slip regulator 13 changes to the first operating mode, as shown in Fig. 4a. In the first operating mode, the controlled variable 13b 5 ernitted by the slip regulator 13 is always identical to the controlled variable 14b of the nitrogen oxide regulator since the proportional path is used in the proportional/integral part 20. so that the output value v is equal to the input value z, w hile the integrator is switched off. This circuit ensures that the controlled value 13b of the slip regulator 13 is always identical to the controlled variable 14b of the nitrogen oxide regulator 14, 0 irrespective of the value x, which is formed from the difference between the nominal treatment medium slip value 9c and the treatment medium slip 9b. In the first operating mode, the controlled variable 13b follows the controlled variable 14b directly and, if necessary, makes a jump when the changeover apparatus 19 s~hitches. The minimum value selection apparatus 12 arranged downstream tries to select the smaller of the two 5 controlled variables 13b, 14b. Since these two values are of equal magnitude in the first operating mode. this ensures that the controlled variable 12b corresponds to thecontrolled variable 14b ofthe nitrogen o~ide regulator 14. Thus~ the supply of ammonia water is now regulated by the nitrogen oxide regulator 14, irrespective of the slip that occurs. so that the control system tries to comply with the required nitrogen 2 0 oxide emission limit~ at the e~cpense of the ammonia slip.
The second operating mode is also designed in particular such that there is no jump in the controlled variable 13b when the changeover apparatus 19 ~switches from z to x. that is to say when it changes over in such a manner that the switch to z is opened and the switch to x is closed. In the second operating mode, an integral 2 5 regulator is connected in the proportional/integral part 20. while a proportional regulator is connected in the proportional part 21, resulting in a so-called PI regulator over311 in the slip regulator 13 in the second operating mode. In this second operatin_ mode~ the slip regulator 13 tries to reduce the difference between the treatment medium slip 9b and the nominal treatment medium slip value 9c to zero. bv producing a 3 o correspondin controlled variable l 3b. In the second operating mode~ the controlled variables 13b and 14b may assume differem values. the minimurn value selection apparatus 12 selecting the smaller of the two values and pre~let~rmining this as the controlled variable 12b for the flow regulator 17.
The second exemplary embodiment of a control apparatus 30~ ~vhich is 5 illustrated in Figure 3, differs from the e.Yemplary embodiment according to Figure 2 in that the nitrogen oxide content is controlled bv means of a cascade control system in that an untreated gas nitrogen oxide content 1 Ob, ~vhich has a more dynarnic response.
is supplied to a subordinate nitrogen oxide regulator 14, and the more inert signal of the pure gas nitrogen oxide content 1 lb is supplied to the superior nitrogen oxide regulator 0 18, this nitrogen oxide regulator 18 producing a controlled variable 1 8b which, with the difference being formed between it and a nominal untreated gas nitrogen oxide content value specified in an input apparatus l Od. producing a preset value for the nitrogen oxide regulator 14. Such a cascade control system has the advantage of better dynamic control response. With the exception of this cascade control system, the hvo control 15 apparatuses 30 according to Fig. 3 and F'ig. ~ are of identical design.
Claims (20)
1. A method for controlling an amount of a treatment medium introduced into a firing apparatus in order to reduce a nitrogen oxide content of exhaust gases from combustion processes comprising the steps of:
- determining a mean nitrogen oxide content of said exhaust gases;
- generating a first control variable as a function of the nitrogen oxide content for controlling the amount of the treatment medium introduced;
- generating a second control variable as a function of a treatment medium slip for controlling the amount of the treatment medium introduced; and - controlling the amount of said treatment medium introduced through a third control variable determined by one of said first control variable and said second control variable.
- determining a mean nitrogen oxide content of said exhaust gases;
- generating a first control variable as a function of the nitrogen oxide content for controlling the amount of the treatment medium introduced;
- generating a second control variable as a function of a treatment medium slip for controlling the amount of the treatment medium introduced; and - controlling the amount of said treatment medium introduced through a third control variable determined by one of said first control variable and said second control variable.
2. A method according to claim 1, wherein the first control variable controls the amount of the treatment medium introduced when the mean nitrogen oxide content exceeds a nominal nitrogen oxide content mean value.
3. A method according to claim 2, comprising the further step of comparing the first control variable and the second control variable to determine which variable has a lower value, wherein the variable having the lower value controls the third control variable.
4. A method according to claim 1. wherein the mean nitrogen oxide content is calculated in accordance with a predetermined method.
5. A method according to claim 1, further comprising the step of measuring the nitrogen oxide content of untreated exhaust gases and treated exhaust gases, wherein the step of generating the first control variable utilizes both nitrogen oxide content exhaust gas measurements.
6. A method according to claim 2, wherein the nominal nitrogen oxide content mean value is less than a predetermined value.
7. A method according to claim 3, wherein the third control variable varies continuously and does not jump to a new value when the control variable having the lower value changes from one variable to the other.
8. A control apparatus for controlling an amount of a treatment medium introduced into a firing apparatus in order to reduce a nitrogen oxide content of exhaust gases from combustion processes, comprising:
- an averaging apparatus for calculating a mean nitrogen oxide content;
- a first nitrogen oxide regulator having a oxide control variable:
- a slip regulator having a slip control variable;
- a flow regulator having a flow control variable for controlling the flow of the treatment medium; and - a changeover apparatus driven by the averaging apparatus;
- wherein said changeover apparatus determines one of the oxide control variable and the slip control variable to be a flow control variable for the flow regulator.
- an averaging apparatus for calculating a mean nitrogen oxide content;
- a first nitrogen oxide regulator having a oxide control variable:
- a slip regulator having a slip control variable;
- a flow regulator having a flow control variable for controlling the flow of the treatment medium; and - a changeover apparatus driven by the averaging apparatus;
- wherein said changeover apparatus determines one of the oxide control variable and the slip control variable to be a flow control variable for the flow regulator.
9. A control apparatus according to claim 8. wherein the oxide control variable and the slip control variable are supplied to a minimum value selection apparatus which supplies the smaller of the oxide and slip control variables as the flow control variable to the flow regulator.
10. A control apparatus according to claim 8, wherein a second nitrogen oxide regulator is connected to said control apparatus upstream of the first nitrogen oxide regulator, forming a cascade control system.
11. A method according to claim 1, comprising the further step of comparing the first control variable and the second control variable. wherein the variable having a lower value controls the third control variable, when the mean nitrogen oxide content does not exceed a nominal nitrogen oxide content mean value.
12. A method according to claim 2, wherein the mean nitrogen oxide content is calculated in accordance with a predetermined method.
13. A method according to claim 3, wherein the mean nitrogen oxide content is calculated in accordance with a predetermined method.
14. A method according to claim 2, further comprising the step of measuring the nitrogen oxide content of both untreated exhaust gases and treated exhaust gases, wherein the step of generating the first control variable utilizes both nitrogen oxide content exhaust gas measurements.
15. A method according to claim 3, further comprising the step of measuring the nitrogen oxide content of untreated exhaust gases and treated exhaust gases, wherein the step of generating the first control variable utilizes both nitrogen oxide content exhaust gas measurements.
16. A method according to claim 4, further comprising the step of measuring the nitrogen oxide content of untreated exhaust gases and treated exhaust gases, wherein the step of generating the first control variable utilizes both nitrogen oxide content measurements.
17. A method according to claim 3, wherein the nominal nitrogen oxide content mean value is less than a predetermined value.
18. A method according to claim 5. wherein the nominal nitrogen oxide content mean value is less than a predetermined value.
19. A method according to claim 5. wherein the nominal nitrogen oxide content mean value is less than a predetermined value.
20. A control apparatus according to claim 9, wherein a second nitrogen oxide regulator is connected to said control apparatus upstream of the first nitrogen oxide regulator, forming a cascade control system.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH0686/97 | 1997-03-21 | ||
| CH68697 | 1997-03-21 |
Publications (1)
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| CA2232721A1 true CA2232721A1 (en) | 1998-09-21 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002232721A Abandoned CA2232721A1 (en) | 1997-03-21 | 1998-03-19 | Method and apparatus for controlling the amount of a treatment medium introduced in order to reduce the nitrogen oxide content of the exhaust gases from combustion processes |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0866395B1 (en) |
| JP (1) | JP3002819B2 (en) |
| KR (1) | KR100294991B1 (en) |
| AT (1) | ATE227029T1 (en) |
| CA (1) | CA2232721A1 (en) |
| CZ (1) | CZ296118B6 (en) |
| DE (1) | DE59806085D1 (en) |
| HU (1) | HUP9800244A2 (en) |
| NO (1) | NO981278L (en) |
| PL (1) | PL325437A1 (en) |
| TW (1) | TW422944B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2005280464B2 (en) * | 2004-08-27 | 2009-12-03 | General Electric Technology Gmbh | Optimized air pollution control |
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|---|---|---|---|---|
| US7166262B2 (en) * | 2002-09-25 | 2007-01-23 | Mitsubishi Power Systems, Inc. | Control for ammonia slip in selective catalytic reduction |
| US7776265B2 (en) | 2004-03-18 | 2010-08-17 | Cummins Filtration Ip, Inc. | System for diagnosing reagent solution quality |
| US7536232B2 (en) | 2004-08-27 | 2009-05-19 | Alstom Technology Ltd | Model predictive control of air pollution control processes |
| US7323036B2 (en) | 2004-08-27 | 2008-01-29 | Alstom Technology Ltd | Maximizing regulatory credits in controlling air pollution |
| US7634417B2 (en) | 2004-08-27 | 2009-12-15 | Alstom Technology Ltd. | Cost based control of air pollution control |
| US7117046B2 (en) * | 2004-08-27 | 2006-10-03 | Alstom Technology Ltd. | Cascaded control of an average value of a process parameter to a desired value |
| DE102011081282A1 (en) * | 2011-08-19 | 2013-02-21 | Siemens Aktiengesellschaft | Method and device for reducing the amount of pollutants in exhaust gases |
| KR101925019B1 (en) | 2018-03-30 | 2018-12-04 | 이선영 | Top wear for enabled to be changed to pet cushions |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5489972A (en) * | 1977-12-28 | 1979-07-17 | Mitsubishi Heavy Ind Ltd | Ammonia flow rate control method in dry exhaust gas denitration process |
| EP0263195B1 (en) * | 1986-10-07 | 1991-03-06 | Nippon Kokan Kabushiki Kaisha | Method and apparatus for controlling denitration of exhaust gas |
| JPS6261622A (en) * | 1985-09-12 | 1987-03-18 | Ishikawajima Harima Heavy Ind Co Ltd | Method for controlling denitration |
| AT385915B (en) * | 1986-07-30 | 1988-06-10 | Jenbacher Werke Ag | METHOD FOR CATALYST CONTROL AND REGULATION |
| JPH0365217A (en) * | 1989-08-01 | 1991-03-20 | Ishikawajima Harima Heavy Ind Co Ltd | Nitrogen oxide control apparatus in flue gas denitrification apparatus |
| WO1992000136A1 (en) * | 1990-06-25 | 1992-01-09 | Occidental Chemical Corporation | Simultaneously reducing dioxins and controlling hydrochloric acid emissions from solid waste incinerators |
| DE4139862A1 (en) * | 1991-12-03 | 1993-06-09 | Martin Gmbh Fuer Umwelt- Und Energietechnik, 8000 Muenchen, De | METHOD FOR REGULATING THE INPUT QUANTITY OF A TREATMENT MEDIUM FOR REDUCING THE NITROGEN OXIDE CONTENT IN THE EXHAUST GASES OF COMBUSTION PROCESSES |
| JP2656418B2 (en) * | 1992-01-14 | 1997-09-24 | 新日本製鐵株式会社 | Method for controlling NOx in flue gas |
| DE4203219A1 (en) * | 1992-02-05 | 1993-08-12 | Basf Ag | METHOD FOR REDUCING NITROGEN OXIDE IN EXHAUST GASES BY CONTROLLED NH (ARROW DOWN) 3 (ARROW DOWN) ADDITION |
| DE4334071C1 (en) * | 1993-10-06 | 1995-02-09 | Siemens Ag | Process for reducing the nitrogen oxide concentration in the exhaust gas of an internal combustion engine or a combustion plant |
| JP3408852B2 (en) * | 1993-12-14 | 2003-05-19 | バブコック日立株式会社 | Nitrogen oxide concentration control denitration method and apparatus |
| JPH09871A (en) * | 1995-06-22 | 1997-01-07 | Babcock Hitachi Kk | Ammonia injection amount control device for a plurality of exhaust gas treatment systems |
-
1998
- 1998-02-05 HU HU9800244A patent/HUP9800244A2/en unknown
- 1998-02-18 DE DE59806085T patent/DE59806085D1/en not_active Expired - Fee Related
- 1998-02-18 AT AT98102765T patent/ATE227029T1/en not_active IP Right Cessation
- 1998-02-18 EP EP98102765A patent/EP0866395B1/en not_active Expired - Lifetime
- 1998-02-24 TW TW087102608A patent/TW422944B/en not_active IP Right Cessation
- 1998-03-13 KR KR1019980008553A patent/KR100294991B1/en not_active IP Right Cessation
- 1998-03-19 CA CA002232721A patent/CA2232721A1/en not_active Abandoned
- 1998-03-19 PL PL98325437A patent/PL325437A1/en unknown
- 1998-03-19 JP JP10070875A patent/JP3002819B2/en not_active Expired - Fee Related
- 1998-03-20 CZ CZ0085498A patent/CZ296118B6/en not_active IP Right Cessation
- 1998-03-20 NO NO981278A patent/NO981278L/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU2005280464B2 (en) * | 2004-08-27 | 2009-12-03 | General Electric Technology Gmbh | Optimized air pollution control |
Also Published As
| Publication number | Publication date |
|---|---|
| NO981278L (en) | 1998-09-22 |
| JPH10263360A (en) | 1998-10-06 |
| KR19980080251A (en) | 1998-11-25 |
| NO981278D0 (en) | 1998-03-20 |
| HUP9800244A2 (en) | 1999-06-28 |
| EP0866395A1 (en) | 1998-09-23 |
| CZ296118B6 (en) | 2006-01-11 |
| EP0866395B1 (en) | 2002-10-30 |
| ATE227029T1 (en) | 2002-11-15 |
| JP3002819B2 (en) | 2000-01-24 |
| HU9800244D0 (en) | 1998-04-28 |
| DE59806085D1 (en) | 2002-12-05 |
| KR100294991B1 (en) | 2001-07-12 |
| TW422944B (en) | 2001-02-21 |
| CZ85498A3 (en) | 1998-10-14 |
| PL325437A1 (en) | 1998-09-28 |
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| EEER | Examination request | ||
| FZDE | Discontinued |