CN213853892U - Flue gas denitration system - Google Patents
Flue gas denitration system Download PDFInfo
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- CN213853892U CN213853892U CN202022457202.2U CN202022457202U CN213853892U CN 213853892 U CN213853892 U CN 213853892U CN 202022457202 U CN202022457202 U CN 202022457202U CN 213853892 U CN213853892 U CN 213853892U
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Abstract
The utility model relates to a flue gas denitration system belongs to flue gas treatment facility technical field, including denitration unit, conveying unit and the control unit. The denitration unit is equipped with flue gas inlet, exhanst gas outlet and aqueous ammonia import. The flue gas inlet and the flue gas outlet are respectively provided with a nitrogen oxide analyzer. The conveying unit is connected with the ammonia water inlet to convey ammonia water. The conveying unit is provided with a flow monitoring device, and a plurality of ammonia water control valves are arranged between the flow monitoring device and the ammonia water inlet in parallel. According to the actual denitration efficiency of the denitration unit and the set denitration efficiency, the control unit is used for outputting the denitration efficiency adjusting value, and the required ammonia water flow is calculated, so that the ammonia water is timely conveyed through the ammonia water control valve. As long as the concentration of the nitrogen oxides at the flue gas inlet is changed, the conveying flow of the ammonia water can be correspondingly adjusted, and the response speed of conveying the ammonia water is greatly improved. According to the control range of different flow delivery, the control precision of ammonia water delivery is effectively improved through the split-range control of the ammonia water control valves connected in parallel.
Description
Technical Field
The utility model relates to a flue gas treatment facility technical field, in particular to flue gas denitration system.
Background
Waste gas, waste water and other waste materials are generated in the production process of products in the industries of petrochemical industry, medicine and the like, the waste materials often contain a large amount of organic matters with complex components, and the organic matters are treated by the processes of incineration, catalytic oxidation, adsorption and the like so as to be thoroughly purified and reach the national and local emission standards. Among them, NOx in the exhaust gas has an important influence on the atmospheric environment. China has strict requirements on the emission concentration limit value of NOx, so that enterprises need to comprehensively treat the waste gas containing the NOx. The denitration technology commonly used at present is Selective Catalytic Reduction (SCR), and ammonia gas or ammonia water can be used as a reducing agent.
The traditional SCR ammonia spraying control mode is to control an ammonia water flow regulating valve through a PID single loop according to the concentration of the nitrogen oxide at the outlet, wherein the target value of the concentration of the nitrogen oxide at the outlet of a reactor is SP (set value), the actual concentration of the nitrogen oxide at the outlet of the reactor is PV (actual measured value), the MV value of the valve opening of the ammonia water is regulated through the difference value of PV-SP, and the valve opening is increased along with the increase of the PV-SP difference value.
However, in the practical application of the control mode, when the concentration of the nitrogen oxide suddenly rises, the concentration of the nitrogen oxide at the outlet of the reactor suddenly rises, and at this time, the ammonia water flow regulating valve is regulated through the PID, so that a period of delay exists, and the excessive emission of the nitrogen oxide is inevitably caused.
In addition, there are special industries in which NO is contained in exhaust gas generated during the production process2The ratio of NO to NO may vary frequently. The traditional denitration method adopts fixed ammonia nitrogen ratio to calculate ammonia consumption, which causes that NO is generated in the prior art2When the ratio of NO to ammonia is largely changed, ammonia is consumedThe amount calculation has large error with the actual condition, which causes excessive or insufficient ammonia injection.
Meanwhile, the single control valve is adopted to control the ammonia water flow. When the fluctuation range of the content of NOx is large and the consumption of ammonia water fluctuates in a small and large interval, the model selection of the control valve has great difficulty. If the control is not accurate, the ammonia water is too large, so that the ammonia escape is increased; the ammonia water amount is too small, and the required denitration efficiency can not be achieved.
SUMMERY OF THE UTILITY MODEL
In order to overcome prior art's defect, especially to at the denitration in-process, the problem that delay and aqueous ammonia quantity control accuracy are poor is adjusted to the aqueous ammonia quantity, the utility model provides a flue gas denitration system sets up nitrogen oxide analysis appearance respectively through the flue gas import and the exhanst gas outlet at the denitration unit, adopts the flow control of the mode control aqueous ammonia of front end control, has reduced the delay that the aqueous ammonia quantity was adjusted, and the control accuracy of aqueous ammonia quantity has been promoted through the separately controlled flow of a plurality of parallelly connected aqueous ammonia control valves simultaneously.
The technical scheme for realizing the purpose is as follows:
the utility model provides a flue gas denitration system, wherein flue gas denitration system includes:
the denitration unit is provided with a flue gas inlet and a flue gas outlet, wherein the flue gas inlet and the flue gas outlet are both provided with a nitrogen oxide analyzer, and a plurality of ammonia water inlets are further distributed between the flue gas inlet and the flue gas outlet;
the conveying unit is used for conveying ammonia water, the conveying unit is communicated with a plurality of ammonia water inlets, the conveying unit is provided with a flow monitoring device, and at least two ammonia water control valves connected in parallel are further arranged between the flow monitoring device and the ammonia water inlets of the conveying unit; and
and the control unit is used for controlling the opening of the ammonia water control valve to respond to the sudden change of the concentration of the nitric oxide at the flue gas inlet of the denitration unit and reduce the delay time of ammonia spraying.
This applicationThe utility model relates to a flue gas denitration system can convert the nitrogen oxide concentration of the flue gas import department of denitration unit and the nitrogen oxide concentration of exhanst gas outlet department into NO simultaneously2And calculating the actual denitration efficiency, outputting a denitration efficiency adjustment value by using a control unit according to the set denitration efficiency of the denitration unit, and combining NH3/NO2、NH3The required ammonia water flow is calculated according to the NO, the flue gas flow, the ammonia escape, the ammonia water concentration and the like, so that the required ammonia water flow can be directly calculated according to the concentration of the nitrogen oxides at the flue gas inlet of the denitration unit, and the calculated value is given to the ammonia water control valve to correspondingly adjust the flow opening, even if the concentration of the nitrogen oxides is suddenly increased or reduced, and NO is added2When the proportion of the ammonia water to NO is suddenly changed, the response speed of the ammonia water is greatly improved compared with the prior regulation of the concentration of the nitrogen oxide at the smoke outlet. In addition, the opening degree of the flow of the ammonia water is adjusted through the plurality of ammonia water control valves connected in parallel, and the ammonia water control valves in different flow control ranges are used for separate control according to the adjustment flow in different ranges, so that the accurate control under large and small ammonia spraying amount can be realized, and the control precision of the flow of the ammonia water is effectively improved. The problem of difficulty in type selection of a single control valve is solved.
Further, the denitration unit is an SCR reactor.
Further, the flow monitoring device is a flow meter.
Furthermore, the ammonia water control valve comprises a first control valve and a second control valve with different flow control ranges, so that the corresponding ammonia water control valves are selected under different ammonia water flow control requirements, the accuracy of ammonia water flow control is improved, and the response speed of ammonia spraying in the denitration unit is improved.
Further, the flow rate control range of the first control valve is 1kg/h to 30kg/h, and the flow rate control range of the second control valve is 30kg/h to 120 kg/h.
Further, the control unit is a PID controller.
Drawings
Fig. 1 is a schematic diagram of a flue gas denitration system according to a preferred embodiment of the present application.
Detailed Description
The invention will be further explained with reference to the drawings and the specific embodiments.
Referring to fig. 1, the utility model provides a flue gas denitration system, wherein flue gas denitration system includes denitration unit 1, conveying unit 2 and the control unit 3.
Among them, the denitration unit 1 is preferably an SCR reactor. The denitration unit 1 is provided with a flue gas inlet 11 and a flue gas outlet 12. The flue gas to be treated enters the SCR reactor through a flue gas inlet 11, and is discharged through a flue gas outlet 12 after denitration treatment. Wherein the flue gas inlet 11 and the flue gas outlet 12 are both provided with a nitrogen oxide analyzer to measure NO and NO at the flue gas inlet 11 and the flue gas outlet 12, respectively2The concentration of (c). Wherein, a plurality of ammonia water inlets 13 are uniformly distributed between the flue gas inlet 11 and the flue gas outlet 12 of the denitration unit 1 so as to supplement ammonia water to the denitration unit 1 to treat flue gas.
Wherein, the control unit 3 is preferably a PID controller to control the opening degree of the ammonia water control valves (FV-1, FV-2) accurately and in time.
A PID controller is a feedback loop component that is common in industrial control applications. The controller compares the collected data to a reference value and then uses the difference to calculate a new input value that is intended to allow the data of the system to reach or remain at the reference value. Different from other simple control operations, the PID controller can adjust the input value according to historical data and the occurrence rate of differences, so that the system is more accurate and more stable. It can be shown mathematically that a PID feedback loop can maintain the stability of the system in the event that other control methods result in a system with a stability error or process iteration.
Ammonia and NO in SCR reactor2The main reaction equation of (2) is:
2NO2+4NH3+O2＝3N2+6H2O
6NO2+8NH3＝7N2+12H2O
4NO+4NH3+O2＝4N2+6H2O
6NO+4NH3＝5N2+6H2O
the concentration of nitrogen oxide at the flue gas inlet 11 and the concentration of nitrogen oxide at the flue gas outlet 12 of the SCR reactor are simultaneously converted into NO2Concentration for subsequent calculation, so that the actual denitration efficiency of the denitration unit 1, namely the removal rate of nitrogen oxides, can be calculated, meanwhile, the control unit 3 is provided with a flue gas outlet 12 nitrogen oxide concentration set value, namely the required denitration efficiency, and the control unit 3 is used for outputting a denitration efficiency adjustment value of-10% according to the actual denitration efficiency and the required denitration efficiency; then combining NH3/NO2、 NH3And calculating the required ammonia water flow rate according to the NO, the flue gas flow rate, the ammonia escape, the ammonia water concentration and the like. Therefore, as long as the concentration of the nitrogen oxides at the flue gas inlet 11 is changed, the required ammonia water flow can be directly calculated through the PID controller according to the actual denitration efficiency and the set denitration efficiency of the SCR reactor, so that the opening degree of the ammonia water control valves (FV-1 and FV-2) can be reasonably controlled.
By using the change of 12 nitrogen oxide concentrations of exhanst gas outlet among the prior art as the reference basis, the utility model discloses the improvement is for using the change of 11 nitrogen oxide concentrations of exhanst gas inlet as the reference basis to reach time control ammonia water control valve (FV-1, FV-2) through the PID controller and carry the aqueous ammonia of reasonable flow, improved the response speed of aqueous ammonia supply when nitrogen oxide concentration breaks suddenly greatly.
Wherein, the conveying unit 2 is communicated with a plurality of ammonia water inlets 13 to convey ammonia water. Wherein the delivery unit 2 is provided with a flow monitoring device 21. Wherein said flow monitoring means 21 is preferably a flow meter. The conveying unit 2 is also provided with a preset number of ammonia water control valves (FV-1, FV-2) connected in parallel between the flow monitoring device 21 and the ammonia water inlet 13. Corresponding ammonia water control valves (FV-1 and FV-2) are selected under different ammonia water flow control requirements to improve the accuracy of ammonia water flow control and improve the response speed of ammonia spraying in the denitration unit 1.
Wherein the ammonia water control valves (FV-1, FV-2) are preferably a first control valve FV-1 and a second control valve FV-2 having different flow control ranges. Wherein, the minimum opening degree 10% of the first control valve FV-1 corresponds to a control flow of 1kg/h, and the maximum opening degree 80% corresponds to a control flow of 30 kg/h. Wherein 25% of the minimum opening degree of the second control valve FV-2 corresponds to a control flow of 30kg/h, and 60% of the maximum opening degree corresponds to a control flow of 120 kg/h.
Wherein the control circuit of the first control valve FV-1 and the second control valve FV-2 are tabulated as follows:
| control valve | PID loop | Minimum opening degree | Large opening degree |
| FV-1 | FIC-001 | 10％→1kg/h | 80％→30kg/h |
| FV-2 | FIC-002 | 25％→30kg/h | 60％→120kg/h |
Specifically, before ammonia spraying of the delivery unit 2, the first control valve FV-1 and the second control valve FV-2 are respectively in an initial state and are all closed;
when the ammonia injection amount of the conveying unit 2 is increased from 1kg/h to 120 kg/h:
1. when the calculated ammonia water usage amount is lower than 30kg/h, selecting a first control valve FV-1 to control the ammonia water conveying precision of the conveying unit 2, and closing a second control valve FV-2;
2. when the calculated ammonia water usage amount is higher than 30kg/h, selecting a second control valve FV-2 to control the ammonia water conveying precision of the conveying unit 2, and closing a first control valve FV-1;
3. when the amount of ammonia water used is calculated to rise to 120kg/h, the opening degree of the second control valve FV-2 is increased to 60%.
When the ammonia injection amount of the conveying unit 2 is reduced from 120kg/h to 1 kg/h:
1. when the calculated ammonia water usage amount is higher than 30kg/h, selecting a second control valve FV-2 to control the ammonia water conveying precision of the conveying unit 2, and closing a first control valve FV-1;
2. when the calculated ammonia water usage amount is lower than 30kg/h, selecting a first control valve FV-1 to control the ammonia water conveying precision of the conveying unit 2, and closing a second control valve FV-2;
3. when the calculated ammonia amount is decreased to 1kg/h, the opening degree of the first control valve FV-1 is decreased to 10%.
It should be noted that the terms "first and second" in the present invention are used for descriptive purposes only, do not denote any order, are not to be construed as indicating or implying any relative importance, and are to be interpreted as names.
The above embodiments are merely preferred embodiments of the present disclosure, which are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like, which are within the spirit and principle of the present disclosure, should be included in the scope of the present disclosure.
Claims (6)
1. A flue gas denitration system, wherein the flue gas denitration system includes:
the denitration unit is provided with a flue gas inlet and a flue gas outlet, wherein the flue gas inlet and the flue gas outlet are both provided with a nitrogen oxide analyzer, and a plurality of ammonia water inlets are further distributed between the flue gas inlet and the flue gas outlet;
the conveying unit is used for conveying ammonia water, the conveying unit is communicated with a plurality of ammonia water inlets, the conveying unit is provided with a flow monitoring device, and at least two ammonia water control valves connected in parallel are further arranged between the flow monitoring device and the ammonia water inlets of the conveying unit; and
and the control unit is used for controlling the opening degree of the ammonia water control valve in time so as to respond to the sudden change of the concentration of the nitric oxide at the flue gas inlet.
2. The flue gas denitration system of claim 1, wherein the denitration unit is an SCR reactor.
3. The flue gas denitration system of claim 1, wherein the flow monitoring device is a flow meter.
4. The flue gas denitration system of claim 1, wherein the ammonia water control valve comprises a first control valve and a second control valve having different flow control ranges.
5. The flue gas denitration system of claim 4, wherein the flow rate control range of the first control valve is 1kg/h to 30kg/h, and the flow rate control range of the second control valve is 30kg/h to 120 kg/h.
6. The flue gas denitration system of claim 1, wherein the control unit is a PID controller.
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| CN202022457202.2U CN213853892U (en) | 2020-10-30 | 2020-10-30 | Flue gas denitration system |
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| CN202022457202.2U CN213853892U (en) | 2020-10-30 | 2020-10-30 | Flue gas denitration system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114682084A (en) * | 2022-03-28 | 2022-07-01 | 西安热工研究院有限公司 | Parallel denitration reducing agent flow adjusting system and method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114682084A (en) * | 2022-03-28 | 2022-07-01 | 西安热工研究院有限公司 | Parallel denitration reducing agent flow adjusting system and method |
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