CN108371888A - Prevent the SCR denitration system control method of urea overspray - Google Patents
Prevent the SCR denitration system control method of urea overspray Download PDFInfo
- Publication number
- CN108371888A CN108371888A CN201810203146.4A CN201810203146A CN108371888A CN 108371888 A CN108371888 A CN 108371888A CN 201810203146 A CN201810203146 A CN 201810203146A CN 108371888 A CN108371888 A CN 108371888A
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- China
- Prior art keywords
- concentration
- urea
- nitrous oxides
- overspray
- oxides concentration
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Classifications
-
- 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
- B01D53/90—Injecting reactants
-
- 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
-
- 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
- G05D11/13—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means
- G05D11/139—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means by measuring a value related to the quantity of the individual components and sensing at least one property of the mixture
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2251/00—Reactants
- B01D2251/20—Reductants
- B01D2251/206—Ammonium compounds
- B01D2251/2067—Urea
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
Abstract
A kind of SCR denitration system control method preventing urea overspray, includes the following steps：Step 1. detects the nitrous oxides concentration of exhaust ports, is less than concentration set point and then enters PID mode, otherwise enters step 2；Step 2. controls urea jet velocity, so that it is increased increase with time, detects the nitrous oxides concentration of exhaust ports, if nitrous oxides concentration reduces increase with time, enters PID mode；Otherwise 3 are entered step；Step 3. reduces urea jet velocity, detects the nitrous oxides concentration of exhaust ports, until after nitrous oxides concentration is less than concentration set point, into PID mode.The present invention is combined control by opened loop control with closed loop PID mode, can be corrected to urea overspray state, so that control model is controlled always towards the minimum nitrous oxides concentration direction of setting, the continuous abnormal of nitrous oxides concentration is avoided to increase.
Description
Technical field
The invention belongs to chemical technology fields, be related to SCR denitration technology, and in particular to a kind of urea overspray that prevents
SCR denitration system control method.
Background technology
SCR denitrations are most ripe gas denitrifying technologies at present, it is method of denitration after a kind of stove, utilizes reducing agent
NH3 or urea selectively react with NOx under metallic catalyst effect and generate N2 and H2O.It is popular in the world
SCR techniques are broadly divided into 2 kinds of ammonia process SCR and urea method SCR.This 2 kinds of methods are all the restoring function to NOx using ammonia,
It is reduced to NOx (mainly NO) to be not much air the N2 and water of influence under the effect of the catalyst, reducing agent is
NH3.SCR method denitration efficiency is high, and relative low price is widely used in domestic and international project, becomes power plant stack gas denitration
Mainstream technology.
Currently, urea injection system is the part of core the most in SCR denitration system, the control technology of urea pump injection
Whether excellent, the efficiency of denitration and the stable type of denitration parameter operation are directly determined.By PID (proportional-integral-differential controls
System) feedback control technology is it is found that when the rigid input coefficient operation of PID functions, deviation e（t）If larger, the control of system exports
Amount U is bigger, and the speed of response of executing agency's positive action is faster so that the deviation rapid drop of value of feedback and desired value, from
And it is rapidly achieved the stability of system operation.But due to the particularity of urea liquid, i.e., the urea of jet atomization is when excessive
The supersaturation of reactive material, nitrogen oxides can be caused to react incomplete instead so that the nitrogen oxygen concentration value of sensor measurement is more
Height, input deviation bigger, as shown in Figure 1, urea jet velocity is with nitrous oxides concentration curve, there are a turning points, in urea
In the case of overspray, PID/feedback control technology is difficult to realize control purpose.
Invention content
To overcome technological deficiency of the existing technology, prevent the SCR of urea overspray de- the invention discloses a kind of
Nitre system control method.
The SCR denitration system control method of the present invention for preventing urea overspray, include the following steps：
Step 1. booting enters PID mode, under PID mode, sets a concentration desired value, compares concentration desired value and concentration
Setting value, select a wherein larger value as under PID mode to the control targe of nitrous oxides concentration；The concentration setting
Value be and the relevant parameter of operating condition；
Step 2. controls urea jet velocity, so that it is increased increase with time, detects the nitrous oxides concentration of exhaust ports, such as
Fruit nitrous oxides concentration reduces increase with time, then maintains under PID mode；Otherwise 3 are entered step；Into after PID mode,
Urea jet velocity is ultimately limited to speed setting value or less；
Step 3. persistently reduces urea jet velocity, detects the nitrous oxides concentration of exhaust ports, until nitrous oxides concentration is small
In concentration set point, PID mode is returned again to.
Preferably, the speed setting value VM=Vbset+D1, wherein Vbset reach for exhaust ports under the conditions of different operating
Corresponding urea jet velocity when to minimum nitrous oxides concentration, D1 are the margin value of a setting.
Preferably, the concentration set point Cmnox=Cnox+D2, wherein Cnox can for exhaust ports under the conditions of different operating
With the minimum nitrous oxides concentration reached, D2 is the margin value of a setting.
Further, the different operating condition is different generated output power.
Further, the control targe of the PID mode is concentration set point.
Using the SCR denitration system control method of the present invention for preventing urea overspray, by opened loop control with close
Ring PID mode combines control, can be corrected to urea overspray state, make control model always towards the minimum nitrogen of setting
Oxide concentration direction is controlled, and the continuous abnormal that the positive feedback under excessive state causes nitrous oxides concentration is avoided to increase.
Description of the drawings
Fig. 1 is urea jet velocity described in background technology and nitrous oxides concentration curve synoptic diagram；
Fig. 2 is to survey certain generator to obtain the minimum nitrous oxides concentration of emission and urea jet velocity curve under different capacity
Schematic diagram；
Fig. 3 is to survey certain generator different capacity and the minimum nitrous oxides concentration curve synoptic diagram of emission；
Fig. 4 is a kind of specific implementation mode stream of the SCR denitration system control method of the present invention for preventing urea overspray
Journey schematic diagram.
Specific implementation mode
Below in conjunction with the accompanying drawings, the specific implementation mode of the present invention is described in further detail.
As shown in Figure 1, after urea jet velocity is more than turning point, due to causing to continue to increase under urea overspray state
Add urea injection that cannot not only reduce discharged nitrous oxides, discharged nitrous oxides can be made to be significantly increased instead, traditional PID mode
It can not control effectively to it, it is linear work area to define on the left of the straight line for passing through turning point in Fig. 1, and right side is non-linear work
Make area.To overcome the defect of traditional control method, the invention discloses a kind of SCR denitration system controls preventing urea overspray
Method processed, includes the following steps：
Step 1. booting enters PID mode, under PID mode, sets a concentration desired value, compares concentration desired value and concentration
Setting value, select a wherein larger value as under PID mode to the control targe of nitrous oxides concentration；The concentration setting
Value be and the relevant parameter of operating condition；
Step 2. controls urea jet velocity, so that it is increased increase with time, detects the nitrous oxides concentration of exhaust ports, such as
Fruit nitrous oxides concentration reduces increase with time, then maintains under PID mode；Otherwise 3 are entered step；Into after PID mode,
Urea jet velocity is ultimately limited to speed setting value or less；
Step 3. persistently reduces urea jet velocity, detects the nitrous oxides concentration of exhaust ports, until nitrous oxides concentration is small
In concentration set point, PID mode is returned again to.
For the present invention is particularly applicable in thermal power generation unit, heat power station burning coal generates vapor and pushes hair
Electricity, for different generated outputs, can be obtained by actual measurement early period at generated output and corresponding gas discharge outlet can reach
The minimum nitrous oxides concentration arrived, the jet velocity of urea and the nitrous oxides concentration of discharge gas are closely related, for difference
When generated output obtains minimum nitrous oxides concentration, corresponding urea jet velocity at this time can be detected.
In certain practical smoke discharging device, system is directly adjusted under urea jet velocity pattern using external, with urine
The reaction consumption of the increase of plain jet velocity, nitrogen oxides increases, and the nitrous oxides concentration of discharge reduces, and records minimum nitrogen
Corresponding value of feedback repeats the above steps for different generator powers when oxide concentration, thus obtain one about
The optimum response efficiency curve of urea injecting quantity.As shown in Figure 1, according to Fig. 1 curves, can obtain under different generator powers
The best emitted dose of urea：
Vbset=K1*P
Wherein K1 is the parameter of curve in Fig. 1, and P indicates generator power.
Fig. 2 is the minimum nitrous oxides concentration curve of corresponding generator power-.It can be obtained in different generator powers by Fig. 2
Under obtain minimum nitrous oxides concentration when being sprayed：
Cnox=1/K2*P
Wherein K2 is the parameter of curve in Fig. 2, and P indicates generator power.
It can be seen that minimum nitrous oxides concentration and corresponding urea jet velocity are only related with generator power,
The constant situation of generator power adjusts nitrous oxides concentration and only needs to adjust urea jet velocity.
At runtime, detection first detects the nitrous oxides concentration of exhaust ports to the present invention, then recognizes less than concentration set point
For the left side linear work area of generator operation turning point shown in Fig. 1, PID mode can be adjusted at this time, and system enters
PID mode, that is, traditional PID mode controls.
A concentration desired value C is set in step 1 firstIt is expected that, compare concentration desired value CIt is expected thatWith concentration set point CMNOX,
Select a wherein larger value as under PID mode to the control targe of nitrous oxides concentration.Concentration desired value is usually one
A external indicator, such as set desired value is required according to power plant's blowdown.Select control of the higher value as PID mode
Target, control process are stablized, and control model will not be frequently replaced.
If nitrous oxides concentration is more than concentration set point, need to further determine whether to be operated in linear work area,
Urea jet velocity is controlled, so that it is increased increase with time, detects the nitrous oxides concentration of exhaust ports, if nitrogen oxides
Concentration reduces increase with time, then meets the linear work area feature in Fig. 1, into PID mode, into after PID mode, and urine
Plain jet velocity should be ultimately limited to speed setting value or less.If nitrous oxides concentration increases with urea jet velocity and is increased
Add, illustrates that the nonlinear operation area that generator operation is shown in Fig. 1 at this time, PID mode no longer work.Control system, which enters, to be opened
Ring MANUAL CONTROL mode is not further added by urea jet velocity, then reduces urea jet velocity, directly controls the injection of urea pump
Speed, and the nitrous oxides concentration of exhaust ports is detected at any time, until nitrous oxides concentration is less than concentration set point, while urinating
After plain jet velocity is less than speed setting value, then operating system enters PID mode.
It can be according to the corresponding urea jet velocity of Curve selection generator power and nitrous oxides concentration of Fig. 1 and Fig. 2
As speed setting value and concentration set point.Speed setting value VM=Vbset+D1 can also be reset；Concentration set point
Cmnox=Cnox+D2, D1, D2 are the adjustable speed for being more than zero and concentration margin value, size according to equipment operating parameter and
The purpose of control accuracy decision, the setting of D1 and D2 is to ensure that control method of the present invention stablizes the working condition of system as possible
It works under PID mode, the frequent switching between PID mode and manual open-loop pattern is reduced, even if systems attempt is operated in Fig. 1
Shown in linear work area；In the present invention, after entering PID mode, that is, PID mode control, PID mode can be selected to nitrogen
The control targe value of oxide concentration is the concentration set point, ensures certain margin of operation, avoids system frequent switching
Into nonlinear operation area.
Using the SCR denitration system control method of the present invention for preventing urea overspray, by opened loop control with close
Ring PID mode combines control, can be corrected to urea overspray state, make control model always towards the minimum nitrogen of setting
Oxide concentration direction is controlled, and the continuous abnormal that the positive feedback under excessive state causes nitrous oxides concentration is avoided to increase.
Previously described each preferred embodiment for the present invention, if the preferred embodiment in each preferred embodiment
It is not apparent contradictory or premised on a certain preferred embodiment, each preferred embodiment can arbitrary stack combinations
Use, the design parameter in the embodiment and embodiment merely to clearly state the invention verification process of inventor, and
It is non-to limit the scope of patent protection of the present invention, scope of patent protection of the invention is still subject to its claims, all
It is equivalent structure variation made by the specification and accompanying drawing content with the present invention, similarly should be included in the protection model of the present invention
In enclosing.
Claims (5)
1. preventing the SCR denitration system control method of urea overspray, it is characterised in that, include the following steps：
Step 1. booting enters PID mode, under PID mode, sets a concentration desired value, compares concentration desired value and concentration
Setting value, select a wherein larger value as under PID mode to the control targe of nitrous oxides concentration；The concentration setting
Value be and the relevant parameter of operating condition；
Step 2. controls urea jet velocity, so that it is increased increase with time, detects the nitrous oxides concentration of exhaust ports, such as
Fruit nitrous oxides concentration reduces increase with time, then maintains under PID mode；Otherwise 3 are entered step；Into after PID mode,
Urea jet velocity is ultimately limited to speed setting value or less；
Step 3. persistently reduces urea jet velocity, detects the nitrous oxides concentration of exhaust ports, until nitrous oxides concentration is small
In concentration set point, PID mode is returned again to.
2. the SCR denitration system control method as described in claim 1 for preventing urea overspray, which is characterized in that described
Speed setting value VM=Vbset+D1, wherein Vbset reach minimum nitrous oxides concentration for exhaust ports under the conditions of different operating
When corresponding urea jet velocity, D1 is the margin value of a setting.
3. preventing the SCR denitration system control method of urea overspray as described in claim 1, which is characterized in that described dense
Spend setting value Cmnox=Cnox+D2, the minimum nitrogen oxides that wherein Cnox can reach for exhaust ports under the conditions of different operating
Concentration, D2 are the margin value of a setting.
4. preventing the SCR denitration system control method of urea overspray as described in Claims 2 or 3, which is characterized in that described
Different operating condition is different generated output power.
5. preventing the SCR denitration system control method of urea overspray as claimed in claim 3, which is characterized in that the PID
The control targe of pattern is concentration set point.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810203146.4A CN108371888A (en) | 2018-03-13 | 2018-03-13 | Prevent the SCR denitration system control method of urea overspray |
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| CN201810203146.4A CN108371888A (en) | 2018-03-13 | 2018-03-13 | Prevent the SCR denitration system control method of urea overspray |
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| CN108371888A true CN108371888A (en) | 2018-08-07 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113617206A (en) * | 2020-05-07 | 2021-11-09 | 江苏海默环保科技有限公司 | Control method of spray gun, control system of spray gun and incineration system |
| CN114100367A (en) * | 2021-10-19 | 2022-03-01 | 国能神福(石狮)发电有限公司 | Denitration control method and device |
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| JP2002273176A (en) * | 2001-03-16 | 2002-09-24 | Tokyo Gas Co Ltd | Method and apparatus for controlling addition amount of reducing agent |
| WO2008078645A1 (en) * | 2006-12-25 | 2008-07-03 | Mitsubishi Fuso Truck And Bus Corporation | Exhaust purifying apparatus for internal combustion engine |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113617206A (en) * | 2020-05-07 | 2021-11-09 | 江苏海默环保科技有限公司 | Control method of spray gun, control system of spray gun and incineration system |
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| CN114100367A (en) * | 2021-10-19 | 2022-03-01 | 国能神福(石狮)发电有限公司 | Denitration control method and device |
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Application publication date: 20180807 |