CN104226110B - Coal-fired boiler SCR (Selective Catalytic Reduction) denitration control method and system - Google Patents
Coal-fired boiler SCR (Selective Catalytic Reduction) denitration control method and system Download PDFInfo
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- CN104226110B CN104226110B CN201410527517.6A CN201410527517A CN104226110B CN 104226110 B CN104226110 B CN 104226110B CN 201410527517 A CN201410527517 A CN 201410527517A CN 104226110 B CN104226110 B CN 104226110B
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Abstract
The invention relates to a coal-fired boiler SCR denitration control method and system. The method includes the steps of monitoring the molar ratio of ammonia and nitrogen in each section in real time before flue gas enters a catalyst, regulating ammonia injection branch pipe remote electric control regulating valves corresponding to each section to control ammonia supply amount of each section in real time according to a preset molar ratio of ammonia and nitrogen, and keeping the actually measured molar ratio of ammonia and nitrogen to be identical to the preset molar ratio of ammonia and nitrogen so as to prevent excessive ammonia injection and ensure even concentration distribution of nitric oxides at a denitration system outlet.
Description
Technical field
Pollutant in Coal Burning Boiler emission treatment field of the present invention, particularly a kind of coal-burning boiler SCR denitration control system.
Background technology
Increasingly strict with thermal power plant's pollutant emission standard, selective-catalytic-reduction denitrified (SCR) turns into coal-fired pot
The essential part of stove, with liquefied ammonia or urea as reducing agent, reduction NOx turns into N to SCR2And H2O, unreacted in course of reaction
Complete NH3Discharged with flue gas in the form of escape ammonia, while a small amount of SO can be produced during coal-fired boiler combustion3, unreacted
NH3And SO3And the water in flue gas occurs combination reaction and generates ammonium hydrogen sulfate (ABS), chemical equation is：By equation understand ammonium hydrogen sulfate reaction rate mainly with flue-gas temperature, flue gas in
Escape NH3Concentration, SO3Concentration and H2O concentration is relevant.
Ammonium hydrogen sulfate is presented gaseous state, liquid, graininess respectively at different temperature.Gaseous state or graininess ammonium hydrogen sulfate meeting
As flue gas flows through air preheater, influence will not be produced on air preheater.And liquid sulfuric acid hydrogen ammonium catches flying dust ability pole
By force, can be combined with the fly ash particle in flue gas, be attached to the dust stratification for being formed on air preheater heat transfer element and melting salt shape, caused
Stifled ash of the burn into of preheater etc., and then influence the heat exchange of preheater and the normal operation of unit.Therefore, ammonia nitrogen is reasonably controlled
Mol ratio and ammonia spraying amount, can control ammonia slip concentration from source, the generation of ammonium hydrogen sulfate is reduced or avoided.
Current SCR denitrating flue gas automatic control modes are broadly divided into three classes.
(1) according to the NH for determining3/ NOx mol ratios are come the gas ammonia flow (efficiency tracking) required for providing.
(2) required gas ammonia flow (concentration tracing) is provided according to the denitrating system exit NOx concentration of setting.
(3) control model based on Neural Network Self-learning.
First two control mode is referred to as traditional control mode, and measurement signal has a hysteresis quality of long period, flue gas with
NH3There is strong nonlinearity in the time complexity under catalyst action, it is difficult to be accurately controlled ammonia spraying amount.Based on neutral net certainly
The control model of study, the integrated learning main state variables information relevant with denitration efficiency, the network model training objective is cigarette
Gas exports deviation minimum between NOx content and setting value, asks for optimal ammonia spraying amount, and the model has adaptivity, self study work(
Can, can be good at solving the deficiency that traditional PID control is brought.
But above-mentioned control mode existing defects include：
1, control extensive：Current SCR system smoke components on-line monitoring system is generally sampled using extraction-type single-point, i.e.,
To multi-channel flue-gas entrance and multi-way outlet, a monitoring point is only set, the representativeness of Monitoring Data is not strong with real-time, ignores
The inhomogeneities of NOx regionals distribution, therefore be easy to produce extensive control in actual control.
2, carry out theoretical calculation according to efficiency tracking or concentration tracing and then control the aperture of the spray total pitch of ammonia, theory meter
Calculating cannot match with the NOx concentration distribution in SCR flow fields all the time, so as to cause NOx removal rate to decline and NH3The phenomenon of escape
Occur.
The content of the invention
It is an object of the invention to provide a kind of coal-burning boiler SCR denitration control method and control system, it is used to solve existing
Control method ammonia spraying amount is not enough or excess problem；Further, additionally it is possible to overcome NOx skewness single-point to sample what is caused
Extensive control problem.
To achieve the above object, the solution of the present invention includes：
A kind of coal-burning boiler SCR denitration control method, detection is counted into NOx concentration and ammonia density in flue gas before catalyst
Calculation obtains ammonia nitrogen mol ratio before catalyst；According to default exhanst gas outlet NOxNOx concentration in flue gas before concentration and entrance catalyst
Difference size, calculate preset ammonia nitrogen mol ratio；With preset ammonia nitrogen mol ratio as desired value, the ammonia nitrogen mol ratio before catalyst is
Feedforward amount, ammonia spraying amount is controlled by automatic control algorithm.
SCR device is divided into some subregions on the vertical cross-section that flue gas advances, the corresponding smoke inlet chamber of each subregion
Room is equipped with before corresponding ammonia-gas spraying device, catalyst ammonia density detection means before NOx concentration detection means and catalyst；Each point
Area is independently acquired and controls.
The ammonia nitrogen mol ratio of each subregion isniIt is i-th ammonia nitrogen mole of subregion
Than,It is NO2Molal quantity,It is NH3Molal quantity,It is ammonia density before catalyst,Before catalyst
NOx concentration；
Each preset ammonia nitrogen mol ratio of subregionIt is NO before SCR catalystxConcentration,It is NO in default exiting flue gasxConcentration.
The automatic control algorithm includes pid algorithm or neural network algorithm.
Coal-burning boiler SCR denitration control system, including the smoke inlet chamber that is sequentially communicated, catalyst chamber, flue gas go out
Oral chamber, coal-burning boiler SCR denitration system is divided into some subregions on the vertical cross-section that flue gas advances, the corresponding cigarette of each subregion
Gas inlet chamber is equipped with ammonia density detection before NOx concentration detection means (2) and catalyst before corresponding ammonia-gas spraying device, catalyst
Device (3)；Also include controller (1), NOx concentration detection means (2) before the catalyst of controller sampling connection each subregion
With ammonia density detection means (3) before catalyst, the ammonia-gas spraying device of control connection each subregion.
Ammonia-gas spraying device includes several nozzles, nozzle connection spray ammonia house steward (5), the spray ammonia branch between spray ammonia house steward and nozzle
Road is provided with regulating valve (4).
The corresponding exhanst gas outlet chamber of each subregion is provided with detection means after the catalyst of NOx concentration in detection gas.
NOx concentration and ammonia density before preset NOx concentration, catalyst are introduced in control of the invention, being capable of maximum journey
The guarantee of degree is not in that spray ammonia is excessive or spray ammonia is not enough, and ammonia consumption is reduced while then making guarantee denitration efficiency.
The real-time monitoring of ammonia nitrogen mol ratio before catalyst, controllable in real time is realized, can effectively control SCR denitration system to export the escaping of ammonia dense
Degree, it is to avoid the equipment fault such as air preheater, deduster and wet denitration system jams, corrosion that ammonia slip concentration is excessively caused,
Drastically increase the security and stability of unit operation.
Further, by whole system subregion, partition zone optimizing control is realized in each subregion independent sample, control, can be made
Each subregion exit NOx concentration value of SCR denitration system is consistent, and reduces exit NOx concentration spread standard deviation, extends catalyst
Service life.
Brief description of the drawings
Fig. 1 is the denitrating system of the embodiment of the present invention 2.
Specific embodiment
The present invention will be further described in detail below in conjunction with the accompanying drawings.
Embodiment 1
Of the invention different from existing control method as a kind of control method, ammonia nitrogen mol ratio is preceding before choosing catalyst
Feedback amount, preset ammonia nitrogen mol ratio is target, and the regulating valve of ammonia-gas spraying device is controlled by automatic control algorithms such as such as PID controls, with
Control ammonia spraying amount.
Specifically, before catalyst ammonia nitrogen mol ratio be catalyst before the ratio between NOx concentration and ammonia density be worth it with corresponding mole
The product of ratio；And preset ammonia nitrogen mol ratio is converted into the difference of NOx concentration and preset NOx concentration before catalyst, before catalyst
The ratio between NOx concentration.
NOx concentration and ammonia density before preset NOx concentration, catalyst are introduced in control, can farthest be ensured
Be not in that spray ammonia is excessive or spray ammonia is not enough, ammonia consumption is reduced while then making guarantee denitration efficiency.
Embodiment 2
As shown in Figure 1 for a kind of coal-burning boiler SCR denitration system of the embodiment of the present invention, including the flue gas being sequentially communicated enter
Oral chamber, catalyst chamber, exhanst gas outlet chamber, coal-burning boiler SCR denitration system are divided on the vertical cross-section that flue gas advances
Some regions, the corresponding smoke inlet chamber in each region is equipped with NOx concentration detection dress before corresponding ammonia-gas spraying device, catalyst
Ammonia density detection means 3 before 2 and catalyst is put, ammonia density detection means 3 is in ammonia-gas spraying device downstream before catalyst.
Ammonia-gas spraying device includes several nozzles, nozzle connection spray ammonia house steward 5, the spray ammonia branch road between spray ammonia house steward and nozzle
It is provided with regulating valve 4.Detection means output signal is connected to controller 1 before catalyst.
After coal-burning boiler denitrating system ammonia-spraying grid 10, flue gas enter catalyst before, install NH3Detected with NOx concentration and filled
Put, for real-time monitoring concentration.Each real-time ammonia nitrogen mol ratio of subregionIn each spray ammonia branch pipe peace
Remote electrically controlled regulating valve, ammonia flow on-Line Monitor Device are filled, being capable of each subregion NH of real-time monitoring3For amount；Entered according to each subregion
Mouth NOx actual measured values and correspondence subregion outlet NOx preset value calculations go out preset ammonia nitrogen mol ratio n 'i。
According to DL/T 260《Coal-fired plant flue gas denitrification apparatus performance acceptance test specification》, each subregion
Ammonia nitrogen mol ratioAccording to process control needs,Level off to zero, therefore(ηiThe denitration efficiency of each subregion,Ammonia slip concentration,It is SCR
NO before catalystxConcentration,It is NO in default exiting flue gasxConcentration).Ammonia nitrogen mol ratio is surveyed as preceding with each subregion
Feedback signal, with preset ammonia nitrogen mol ratio as desired value, by PLC or DCS (PID or with the control based on Neural Network Self-learning
Pattern) each subregion correspondence spray remote electrically controlled regulating valve of ammonia subregion is automatically controlled, make actual measurement ammonia nitrogen mol ratio with preset ammonia nitrogen mole
Than consistent, i.e. n=n 'i=ηi, reach the purpose of ammonia spraying amount optimization.
As other embodiment, it is also an option that other formula calculate ammonia nitrogen mol ratio, such as formula is deformed
Or inlet coefficient etc..
In order to detect exhanst gas outlet situation, the NOx concentration in the corresponding exhanst gas outlet chamber of each subregion is provided with detection gas
Catalyst after detection means.
Specific embodiment is presented above, but the present invention is not limited to described implementation method.Base of the invention
This thinking is above-mentioned basic scheme, and for those of ordinary skill in the art, various changes are designed in teaching of the invention
The model of shape, formula, parameter simultaneously need not spend creative work.It is right without departing from the principles and spirit of the present invention
Change, modification, replacement and the modification that implementation method is carried out are still fallen within protection scope of the present invention.
Claims (4)
1. a kind of coal-burning boiler SCR denitration control method, it is characterised in that
Detection is calculated ammonia nitrogen mol ratio before catalyst into NOx concentration and ammonia density in flue gas before catalyst；
According to default exhanst gas outlet NOxConcentration and the difference size into NOx concentration in flue gas before catalyst, calculate preset ammonia
Nitrogen mol ratio；
With preset ammonia nitrogen mol ratio as desired value, the ammonia nitrogen mol ratio before catalyst is feedforward amount, by automatic control algorithm control
Ammonia spraying amount processed.
2. a kind of coal-burning boiler SCR denitration control method according to claim 1, it is characterised in that by SCR device in cigarette
It is divided into some subregions on the vertical cross-section that gas advances, the corresponding smoke inlet chamber of each subregion is equipped with corresponding spray ammonia dress
Put, ammonia density detection means before NOx concentration detection means and catalyst before catalyst；Each subregion is independently acquired and controls
System.
3. a kind of coal-burning boiler SCR denitration control method according to claim 2, it is characterised in that each subregion
Ammonia nitrogen mol ratio isniIt is i-th ammonia nitrogen mol ratio of subregion,It is NO2Molal quantity,It is NH3Molal quantity,It is ammonia density before catalyst,It is NOx concentration before catalyst；
Each preset ammonia nitrogen mol ratio of subregion It is NO before SCR catalystxConcentration,It is NO in default exiting flue gasxConcentration.
4. a kind of coal-burning boiler SCR denitration control method according to claim 1, it is characterised in that described to automatically control
Algorithm includes pid algorithm or neural network algorithm.
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| CN104826492B (en) * | 2015-04-23 | 2017-02-22 | 华北电力大学（保定） | Improvement method for selective catalytic reduction flue gas denitrification and ammonia injection control system |
| CN104841271A (en) * | 2015-05-27 | 2015-08-19 | 山东应天节能环保科技有限公司 | Desulfurization and denitrification automatic control system |
| CN105045089A (en) * | 2015-06-19 | 2015-11-11 | 大唐华银电力股份有限公司金竹山火力发电分公司 | Boiler denitration control method based on outlet NOx content control and system thereof |
| CN104965021B (en) * | 2015-07-24 | 2018-05-04 | 中国科学院重庆绿色智能技术研究院 | A kind of coal-fired flue gas denitration catalyst performance evaluation device and method |
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