SNCR denitration automatic control system

Abstract

The utility model discloses an SNCR (selective non-catalytic reduction) denitration automatic control system which comprises an ammonia water storage and supply system, a desalting water system, a control system, a metering and mixing system, a fire-fighting spraying and ammonia gas leakage alarm system and a distribution injection system, the ammonia water storage and supply system comprises an ammonia water storage tank; the demineralized water system comprises a demineralized water tank; the inlet end of the ammonia water storage tank is connected with an ammonia water mother pipe electric switch valve, the outlet end of the ammonia water storage tank is connected with the inlet end of the ammonia water conveying pump, and the outlet end of the ammonia water conveying pump is connected with the metering and mixing system; the inlet end of the demineralized water tank is connected with the demineralized water main pipe electric switch valve, the outlet end of the demineralized water tank is connected with the inlet end of the demineralized water delivery pump, and the outlet end of the demineralized water delivery pump is connected with the metering and mixing system; according to the device, ammonia water and demineralized water can be fully automatically, efficiently and accurately mixed, and the mixed liquid is accurately and efficiently sprayed into a hearth, so that manpower and resources are saved, the production efficiency is improved, and the enterprise cost is reduced.

Description

Technical Field

[0001] This utility model belongs to the field of flue gas treatment technology, specifically relating to an SNCR denitrification automatic control system. Background Technology

[0002] The statements in this section are merely background information related to this utility model and do not necessarily constitute prior art.

[0003] Nitrogen oxides (NOx) are easily affected by acid rain and photochemical smog, which can damage the ozone layer and pose serious threats to the environment and human health. In recent years, total NOx emissions have remained high, with coal-fired power plants being the largest emitter. Statistics show that 60% of NOx emissions come from coal combustion, with coal-fired power plants accounting for 70% of this consumption. Therefore, boilers in coal-fired power plants must adopt denitrification systems to comprehensively address and control NOx emissions.

[0004] Currently, commonly used denitrification processes include Selective Non-Catalytic Reduction (SNCR) and Selective Catalytic Reduction (SCR), as well as the combined SNCR / SCR flue gas denitrification technology developed from these two. However, the most widely used is the SNCR (Selective Non-Catalytic Reduction) denitrification process. This process reduces nitrogen oxides in flue gas to harmless nitrogen and water using a reducing agent in the absence of a catalyst. First, an ammonia-containing reducing agent is injected into a suitable temperature zone within the furnace. At high temperatures, the reducing agent rapidly decomposes into ammonia, which then reacts with the nitrogen oxides in the flue gas to produce nitrogen and water.

[0005] The inventors discovered that the SNCR denitrification process cannot be fully automated in practical applications and requires manual intervention, including starting and stopping the delivery pump, adjusting the flow rate, and disassembling and assembling the spray gun. This not only consumes manpower, but also the errors and deviations that occur during operation can affect the SNCR denitrification effect, thereby affecting the company's environmental protection indicators. Utility Model Content

[0006] To address the aforementioned issues, this invention provides an SNCR denitrification automatic control system that can fully automate the efficient and precise mixing of ammonia and demineralized water, and accurately and efficiently spray the mixture into the furnace, thereby saving manpower and resources, improving production efficiency, and reducing enterprise costs.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An SNCR denitrification automatic control system includes an ammonia water storage and supply system, a demineralized water system, a control system, a metering and mixing system, a fire sprinkler and ammonia leak alarm system, and a distribution and spraying system; the ammonia water storage and supply system includes an ammonia water storage tank; the demineralized water system includes a demineralized water tank.

[0009] The inlet of the ammonia storage tank is connected to the electric switch valve of the ammonia main pipe, and the outlet of the ammonia storage tank is connected to the inlet of the ammonia delivery pump. The outlet of the ammonia delivery pump is connected to the metering and mixing system. The inlet of the demineralized water tank is connected to the electric switch valve of the demineralized water main pipe, and the outlet of the demineralized water tank is connected to the inlet of the demineralized water delivery pump. The outlet of the demineralized water delivery pump is connected to the metering and mixing system. The outlet of the metering and mixing system is connected to the metering and mixing outlet mass flow meter, and the metering and mixing outlet mass flow meter is connected to the distribution and injection system.

[0010] Furthermore, an ammonia water level gauge is installed on the ammonia water storage tank, and an ammonia water pump outlet reflux electric regulating valve is installed at one end of the ammonia water storage tank; one end of the ammonia water pump outlet reflux electric regulating valve is connected to the ammonia water storage tank, and the other end is connected to the outlet end of the ammonia water delivery pump.

[0011] Furthermore, the outlet end of the ammonia water delivery pump is equipped with an ammonia water pump outlet pressure sensor, and the ammonia water pump outlet reflux electric regulating valve controls the ammonia water pump outlet pressure sensor.

[0012] Furthermore, a demineralized water tank level gauge is installed on the demineralized water tank, and a demineralized water pump outlet reflux electric regulating valve is installed at one end of the demineralized water tank; one end of the demineralized water pump outlet reflux electric regulating valve is connected to the demineralized water tank, and the other end is connected to the outlet end of the demineralized water transfer pump.

[0013] Furthermore, the outlet end of the demineralized water transfer pump is equipped with a demineralized water pump outlet pressure sensor, and the demineralized water pump outlet reflux electric regulating valve controls the demineralized water pump outlet pressure sensor.

[0014] Furthermore, the metering and mixing system includes a metering and mixing demineralized water vortex flow meter, a metering and mixing demineralized water electric regulating valve, a metering and mixing ammonia water electromagnetic flow meter, and a metering and mixing concentrated ammonia water electric regulating valve.

[0015] The metering mixed demineralized water vortex flow meter and the metering mixed demineralized water electric regulating valve are connected, and the outlet end of the metering mixed demineralized water electric regulating valve is connected to the metering mixed outlet mass flow meter; the metering mixed ammonia water electromagnetic flow meter and the metering mixed concentrated ammonia water electric regulating valve are connected.

[0016] Furthermore, the distribution spray system includes a freely retractable dual-fluid spray gun and an electric regulating valve for dilute ammonia water in the spray gun, with several of the freely retractable dual-fluid spray gun and the electric regulating valve for dilute ammonia water in the spray gun arranged at intervals; the freely retractable dual-fluid spray gun and the electric regulating valve for dilute ammonia water in the spray gun are connected; the freely retractable dual-fluid spray gun is connected to an induced draft fan.

[0017] Furthermore, the distribution injection system is connected to the outlet end of the compressed air main pipe electric regulating valve, the inlet end of the compressed air main pipe electric regulating valve is connected to the compressed air pipeline, and a compressed air main pipe pressure sensor is installed on the pipeline connecting the compressed air main pipe electric regulating valve and the distribution injection system.

[0018] Furthermore, the fire sprinkler and ammonia leak alarm system includes an ammonia leak alarm, an electric switch valve for the fire water main pipe, ammonia water storage tank sprinkler coils, and water mist nozzles;

[0019] The ammonia storage tank is equipped with an ammonia leak alarm, which is electrically connected to the fire hydrant main pipe electric switch valve, which is installed on the fire hydrant pipe; both the ammonia leak alarm and the fire hydrant main pipe electric switch valve are electrically connected to the control system.

[0020] Furthermore, the control system is electrically connected to the ammonia escape online monitoring and analysis instrument.

[0021] Compared with the prior art, the advantages and positive effects of this utility model are:

[0022] This invention controls various valves through a control system, enabling automatic activation and deactivation of SNCR denitrification without human intervention. When the boiler induced draft fan starts, the free-retractable dual-fluid spray gun automatically inserts into the furnace upon receiving a signal. Simultaneously, the ammonia water delivery pump starts, followed by the demineralized water delivery pump. The flow regulating valve of the ammonia water pipeline in the metering and mixing system adjusts based on feedback from the online monitoring analyzer. The flow regulating valve of the demineralized water pipeline in the metering and mixing system dilutes the 20% concentrated ammonia water to 5% dilute ammonia water according to a 3:1 ratio between the vortex flow meter of the demineralized water pipeline and the electromagnetic flow meter of the ammonia water pipeline. The mass flow meter at the synchronous metering and mixing outlet displays the value after it is evenly distributed according to the number of spray guns. The flow regulating valve of each spray gun automatically tracks the evenly distributed value, and this value is also displayed in the flow meter. The entire system is then fully activated.

[0023] When the system needs to be shut down, the boiler induced draft fan stops running, the spray guns receive a signal and withdraw from the furnace, and simultaneously the ammonia water delivery pump and the demineralized water delivery pump stop; all regulating valves close according to interlocking mechanisms. The entire system shutdown is then complete; the entire process is fully automated, highly efficient and precise, saving manpower and resources, improving production efficiency, and reducing enterprise costs. Attached Figure Description

[0024] The accompanying drawings, which form part of this specification, are used to provide a further understanding of this utility model. The illustrative embodiments of this utility model and their descriptions are used to explain this utility model and do not constitute an improper limitation of this utility model.

[0025] Figure 1 This is a structural diagram of the SNCR denitrification automatic control system of this utility model;

[0026] In the diagram: 1. Electric on / off valve for ammonia water main pipe; 2. Ammonia water storage tank level gauge; 3. Electric on / off valve for demineralized water main pipe; 4. Demineralized water tank level gauge; 5. Ammonia water transfer pump; 6. Demineralized water transfer pump; 7. Ammonia water storage tank; 8. Demineralized water tank; 9. Electric on / off valve for fire water main pipe; 10. Vortex flow meter for metering mixed demineralized water; 11. Electric regulating valve for metering mixed demineralized water; 12. Electromagnetic flow meter for metering mixed ammonia water; 13. Electric regulating valve for metering mixed concentrated ammonia water; 14. Mass flow meter for metering mixed outlet. 15. Ammonia pump outlet reflux electric regulating valve; 16. Ammonia pump outlet pressure sensor; 17. Demineralized water pump outlet reflux electric regulating valve; 18. Demineralized water pump outlet pressure sensor; 19. Freely retractable dual-fluid spray gun; 20. Spray gun dilute ammonia electric regulating valve; 21. Compressed air main pipe electric regulating valve; 22. Compressed air main pipe pressure sensor; 23. CEMS online monitoring and analysis instrument; 24. Ammonia escape online monitoring and analysis instrument; 25. Exhaust fan; 26. Ammonia leak alarm. Detailed Implementation

[0027] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] The present invention will now be described in detail with reference to the accompanying drawings. This embodiment discloses an automatic SNCR denitrification control system, such as... Figure 1 As shown, it includes an ammonia storage and supply system, a demineralized water system, a control system, a metering and mixing system, a fire sprinkler and ammonia leak alarm system, and a distribution and spraying system; the ammonia storage and supply system includes an ammonia storage tank 7; the demineralized water system includes a demineralized water tank 8;

[0029] The inlet of ammonia storage tank 7 is connected to the electric switch valve 1 of the ammonia main pipe, the outlet of ammonia storage tank 7 is connected to the inlet of ammonia transfer pump 5, and the outlet of ammonia transfer pump 5 is connected to the metering and mixing system; the inlet of demineralized water tank 8 is connected to the electric switch valve 3 of the demineralized water main pipe, the outlet of demineralized water tank 8 is connected to the inlet of demineralized water transfer pump 6, and the outlet of demineralized water transfer pump 6 is connected to the metering and mixing system; the outlet of the metering and mixing system is connected to the metering and mixing outlet mass flow meter 14, and the metering and mixing outlet mass flow meter 14 is connected to the distribution and injection system.

[0030] Specifically, a DCS / PLC distributed control system is adopted, with the DCS manufacturer configuring it to achieve automatic operation. This is implemented after configuration according to the process logic. Each valve is controlled by the control system, which can be a PLC control system, a current technology. Automatic SNCR denitrification can be started and stopped without human intervention. When the boiler induced draft fan 25 starts, the free-retractable dual-fluid spray gun 19 receives a signal and automatically inserts into the furnace. Simultaneously, the ammonia water delivery pump 5 starts, followed by the demineralized water delivery pump 6. The flow regulating valve of the ammonia water pipeline in the metering and mixing system adjusts based on feedback from the online monitoring analyzer. The flow regulating valve of the demineralized water pipeline in the metering and mixing system dilutes the 20% concentrated ammonia water to 5% dilute ammonia water according to a 3:1 ratio between the vortex flow meter of the demineralized water pipeline and the electromagnetic flow meter of the ammonia water pipeline. The mass flow meter at the synchronous metering and mixing outlet displays the value after it is evenly distributed according to the number of spray guns. The flow regulating valve of each spray gun automatically tracks the evenly distributed value, and this value is also displayed in the flow meter. The entire system is then fully operational.

[0031] When the system needs to be shut down, the boiler induced draft fan 25 stops running, the spray gun receives a signal and exits the furnace, and simultaneously the ammonia water transfer pump 5 and the demineralized water transfer pump 6 stop; all regulating valves close according to interlocking. The entire system is shut down; the whole process is fully automated, highly efficient and precise, saving manpower and resources, improving production efficiency, and reducing enterprise costs.

[0032] An ammonia storage tank 7 is equipped with an ammonia storage tank level gauge 2. An ammonia pump outlet reflux electric regulating valve 15 is installed at one end of the ammonia storage tank 7. One end of the ammonia pump outlet reflux electric regulating valve 15 is connected to the ammonia storage tank 7, and the other end is connected to the outlet end of the ammonia transfer pump 5. An ammonia pump outlet pressure sensor 16 is installed at the outlet end of the ammonia transfer pump 5, and the ammonia pump outlet reflux electric regulating valve 15 controls the ammonia pump outlet pressure sensor 16.

[0033] The ammonia storage tank 7 is equipped with a magnetic level gauge, which is interlocked with the electric switch valve 1 of the ammonia main pipe. When the tank level is lower than a certain value, the valve opens automatically; when the tank level is higher than a certain value, the valve closes automatically. This achieves automatic control of the ammonia storage capacity, ensuring a sufficient supply of ammonia and preventing the ammonia transfer pump 5 from running dry.

[0034] The ammonia water delivery pump 5 is interlocked with the automatic telescopic spray gun. When the automatic telescopic spray gun is inserted into the furnace, the ammonia water delivery pump 5 starts; when the automatic telescopic spray gun is withdrawn from the furnace, the ammonia water delivery pump 5 stops; thus realizing the automatic control of ammonia water delivery.

[0035] To ensure that the pressure at the outlet of the ammonia water transfer pump 5 is maintained at a certain value (around 1.0 MPa under normal operating conditions), it is necessary to adjust it through the backflow pressure regulating valve. The pressure regulating valve is interlocked with the pressure transmitter at the pump outlet. This ensures that while the inlet ammonia water pressure changes, the pump outlet pressure remains constant, thereby ensuring the solution pressure at the spray gun inlet and achieving the required spraying effect.

[0036] Ammonia storage tank 7 is a 20% ammonia storage tank. The 20% ammonia storage tank area needs to be designed with a sunshade and a dike. Since ammonia water is prone to volatilization and the volatilization rate increases with rising temperature and prolonged storage time, a safety fire sprinkler system is installed on the top of the sunshade. When the ammonia leakage alarm detects an ammonia leak, it automatically interlocks the electric switch valve of the fire water header. After the valve opens, water mist nozzles evenly distributed around the ammonia storage tank spray dilution water to prevent ammonia volatilization and leakage. At the same time, eyewash stations and wastewater collection pits are set up in the ammonia storage area.

[0037] The technical performance and configuration of the ammonia water transfer pump 5 and the demineralized water transfer pump 6 can affect the operation of the entire denitrification system. For SNCR denitrification, multi-stage vertical centrifugal pumps with low flow rates but high heads are generally preferred, with approximately 25 to 30 stages. Since the pressure of the reducing agent at the inlet of the automatic telescopic spray gun in SNCR denitrification is required to be around 0.5 MPa, considering backflow, pipeline friction and local losses, and based on past engineering experience, the pump head should be selected between 130 and 150 meters. Therefore, the rated pressure at the pump outlet generally needs to be controlled at around 1.0 MPa, and should not be too high or too low. During operation, the backflow electric regulating valve and the pump outlet pressure sensor are interlocked to maintain a stable pump outlet pressure of around 1.0 MPa. Only under the premise of stable and controllable pressure and flow in the pipeline can the atomization effect of the spray gun be guaranteed, thus improving the denitrification efficiency.

[0038] The metering and mixing system primarily dilutes a 20% concentrated ammonia solution with demineralized water in a mixer to a concentration of less than 5%. The required amount of 20% ammonia solution is controlled by an ammonia flow meter and regulated by an electric ammonia regulating valve. The required amount of demineralized water is mixed with the 20% concentrated ammonia solution at a ratio of 3:1. The demineralized water is controlled by a demineralized water flow meter and regulated by an electric demineralized water regulating valve. This ensures that the 20% concentrated ammonia solution can be diluted to a 5% concentration. The mixed dilute ammonia solution is then connected to the distribution and injection system via a mass flow meter.

[0039] The control system of an SNCR denitrification system generally adopts a DCS / PLC. A CEMS online monitoring and analysis instrument is installed in the boiler tail flue. The control system can automatically adjust the ammonia water electric regulating valve in the metering and mixing system according to the NOx concentration signal uploaded by the CEMS online monitoring and analysis instrument. The ammonia water flow meter displays the real-time flow. The demineralized water regulating valve in the metering and mixing system tracks the mixing ratio of demineralized water vortex flow meter and ammonia water electromagnetic flow meter in real time according to a 3:1 ratio. Real-time tracking is realized by DCS configuration according to process logic, which can realize automatic control of the amount of ammonia water added, thereby achieving real-time compliance with NOx emission standards.

[0040] A demineralized water tank level gauge 4 is installed on the demineralized water tank 8. A demineralized water pump outlet reflux electric regulating valve 17 is installed at one end of the demineralized water tank 8. One end of the demineralized water pump outlet reflux electric regulating valve 17 is connected to the demineralized water tank 8, and the other end is connected to the outlet end of the demineralized water transfer pump 6. A demineralized water pump outlet pressure sensor 18 is installed at the outlet end of the demineralized water transfer pump 6, and the demineralized water pump outlet reflux electric regulating valve 17 controls the demineralized water pump outlet pressure sensor 18.

[0041] The demineralized water tank 8 is equipped with a magnetic level gauge, which is interlocked with the electric switch valve for demineralized water injection. When the water level in the tank is lower than a certain value, the valve opens automatically; when the water level in the tank is higher than a certain value, the valve closes automatically. This achieves automatic control of the capacity of the demineralized water tank 8, ensuring a sufficient supply of demineralized water and preventing the demineralized water transfer pump 6 from running dry.

[0042] The demineralized water transfer pump 6 and the ammonia water transfer pump 5 are interlocked. When the ammonia water transfer pump 5 starts, the demineralized water transfer pump 6 starts in an interlocked manner; when the ammonia water transfer pump 5 stops running, the demineralized water transfer pump 6 stops in an interlocked manner; thus realizing automatic control of demineralized water transfer.

[0043] The demineralized water system is used to transport the demineralized water in the demineralized water tank 8 to the metering and mixing system to mix and dilute it with 20% ammonia water to a concentration of 5%-8%, and then spray it into the furnace through the distribution and injection system to participate in the reaction; therefore, the demineralized water delivery pump 6 and the ammonia water delivery pump 5 are interlocked.

[0044] To ensure that the pressure at the outlet of the demineralized water transfer pump 6 is maintained at a certain value (around 1.0 MPa under normal operating conditions), it needs to be adjusted by the backflow pressure regulating valve. The pressure regulating valve is interlocked with the pressure transmitter at the pump outlet. This ensures that while the inlet dilution water pressure changes, the pump outlet pressure remains constant, thereby ensuring the solution pressure at the spray gun inlet and achieving the required spraying effect.

[0045] The metering and mixing system includes a metering and mixing demineralized water vortex flow meter 10, a metering and mixing demineralized water electric regulating valve 11, a metering and mixing ammonia water electromagnetic flow meter 12, and a metering and mixing concentrated ammonia water electric regulating valve 13; the metering and mixing demineralized water vortex flow meter 10 and the metering and mixing demineralized water electric regulating valve 11 are connected, and the outlet end of the metering and mixing demineralized water electric regulating valve 11 is connected to the metering and mixing outlet mass flow meter 14; the metering and mixing ammonia water electromagnetic flow meter 12 and the metering and mixing concentrated ammonia water electric regulating valve 13 are connected.

[0046] The electric regulating valve and electromagnetic flow meter at the outlet of ammonia water transfer pump 5, and the electric regulating valve and vortex flow meter at the outlet of demineralized water transfer pump 6; the metering system needs to dilute the 20% ammonia water supplied from ammonia water transfer pump 5 and the demineralized water supplied from demineralized water transfer pump 6 into a 5%-8% concentration of dilute ammonia water in a mixer, and then inject it into the furnace through the distribution injection system to participate in the reaction.

[0047] The distribution injection system includes a freely retractable dual-fluid spray gun 19 and an electrically adjustable ammonia-water spray gun valve 20. Several freely retractable dual-fluid spray guns 19 and 20 are spaced apart. The freely retractable dual-fluid spray guns 19 and 20 are connected. The freely retractable dual-fluid spray gun 19 is also connected to an induced draft fan 25. The distribution injection system is connected to the outlet end of an electrically adjustable valve 21 on the compressed air main pipe. The inlet end of the electrically adjustable valve 21 is connected to a compressed air pipeline. A compressed air main pipe pressure sensor 22 is installed on the pipeline connecting the electrically adjustable valve 21 and the distribution injection system.

[0048] The automatic telescopic dual-fluid spray gun is interlocked with the boiler outlet induced draft fan 25. When the boiler induced draft fan 25 starts, the automatic telescopic dual-fluid spray gun automatically inserts into the furnace; when the boiler induced draft fan 25 stops running, the spray gun automatically retracts from the furnace.

[0049] The electrically controlled flow regulating valve on each spray gun is interlocked with the mass flow meter at the outlet of the metering and mixing system. The mass flow meter reading is the total flow, which is then evenly distributed among the spray guns, and the value is displayed on the flow meter of each spray gun. For example, this system has 6 spray guns, and the flow rate of each spray gun is 1 / 6 of the mass flow count value; the electrically controlled flow regulating valve on each spray gun automatically tracks this value.

[0050] The flow rate of each spray gun can be remotely controlled and monitored through the electric regulating valve and electromagnetic flow meter on each spray gun, thus achieving precise control of the flow rate of each spray gun. The arrangement and installation position of the spray guns can be ultimately determined based on the distribution of NOx concentration, temperature, airflow and flue gas components in the furnace.

[0051] The electric regulating valve of the compressed air pipeline is interlocked with the pressure transmitter. Under normal operating conditions, the compressed air pressure of the spray gun is not lower than 0.35 MPa and not higher than 0.6 MPa. When the pressure is too low or too high, the electric regulating valve automatically adjusts and maintains the pressure.

[0052] Under normal operating conditions, the standard for ammonia slip in SNCR denitrification is 8 ppm. When the ammonia slip index of the online monitoring and analysis instrument at the boiler outlet exceeds the standard, the amount of ammonia water injected is controlled by the electric regulating valve on each spray gun to reduce the ammonia slip index.

[0053] The fire sprinkler and ammonia leak alarm system includes an ammonia leak alarm 26, an electric switch valve 9 for the fire water main pipe, ammonia water storage tank sprinkler coils and water mist nozzles; the ammonia water storage tank sprinkler coils and water mist nozzles are arranged in a ring around the top of the ammonia water tank.

[0054] The ammonia storage tank 7 is equipped with an ammonia leak alarm 26, which is electrically connected to the fire water main pipe electric switch valve 9, which is installed on the fire water pipe; both the ammonia leak alarm 26 and the fire water main pipe electric switch valve 9 are electrically connected to the control system.

[0055] When a certain amount of ammonia leaks, the ammonia leak alarm is triggered. The ammonia leak alarm is interlocked with the electric switch valve 9 of the fire water main pipe. The electric switch valve is activated to cool and dilute the ammonia in the ammonia area through the spray coil and water mist nozzles to prevent ammonia escape.

[0056] The control system is electrically connected to the ammonia escape online monitoring and analysis instrument 24.

[0057] Current SNCR denitrification designs are prone to causing excessive ammonia slip. Unreacted ammonia (slipped ammonia) will generate ammonium bisulfate. Ammonium bisulfate is a highly viscous substance that can severely damage heat exchangers, significantly impacting their lifespan and increasing operating costs. Therefore, it is necessary to install an online ammonia slip monitoring and analysis instrument 24 in the boiler tail flue. The control system DCS / PLC can use the NH3 concentration signal uploaded by the online ammonia slip monitoring and analysis instrument 24 to control the ammonia water injection volume by adjusting the electric regulating valve 20 on each spray gun of the distribution injection system to reduce ammonia slip.

[0058] The ammonia water electric regulating valve is interlocked with the NOx value shown on the CEMS online monitoring and analysis instrument 23 at the boiler outlet. The NOx concentration is controlled to be <50mg / Nm3 (6% O2, this value is set to be adjustable). When the NOx concentration is higher or lower than the set value, the opening of the ammonia water electric regulating valve can be adjusted accordingly. At the same time, the value of the ammonia water flow meter also changes with the change of the regulating valve opening.

[0059] When the ammonia water electric regulating valve is activated, the electromagnetic flow meter will display the 20% ammonia water flow rate. The demineralized water electric regulating valve automatically tracks the electromagnetic flow count value of the 20% concentrated ammonia water pipeline. At the same time, the demineralized water regulating valve adjusts the value of the vortex flow meter of the demineralized water pipeline according to a 3:1 ratio. The demineralized water and 20% ammonia water are adjusted to a 3:1 ratio, and the final mixed concentration is 5%. Of course, the ratio can also be adjusted according to the actual required ammonia water dilution concentration, which is highly flexible.

[0060] Although the specific embodiments of the present utility model have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present utility model. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solution of the present utility model are still within the scope of protection of the present utility model.

Claims

1. An automatic control system for SNCR denitrification, characterized in that, It includes an ammonia storage and supply system, a demineralized water system, a control system, a metering and mixing system, a fire sprinkler and ammonia leak alarm system, and a distribution and spraying system; the ammonia storage and supply system includes an ammonia storage tank; the demineralized water system includes a demineralized water tank. The inlet of the ammonia storage tank is connected to the electric switch valve of the ammonia main pipe, and the outlet of the ammonia storage tank is connected to the inlet of the ammonia delivery pump. The outlet of the ammonia delivery pump is connected to the metering and mixing system. The inlet of the demineralized water tank is connected to the electric switch valve of the demineralized water main pipe, and the outlet of the demineralized water tank is connected to the inlet of the demineralized water delivery pump. The outlet of the demineralized water delivery pump is connected to the metering and mixing system. The outlet of the metering and mixing system is connected to the metering and mixing outlet mass flow meter, and the metering and mixing outlet mass flow meter is connected to the distribution and injection system. The distribution spray system includes a free-retractable dual-fluid spray gun and an electric regulating valve for dilute ammonia water in the spray gun. Several free-retractable dual-fluid spray guns and electric regulating valves for dilute ammonia water in the spray gun are arranged at intervals. The free-retractable dual-fluid spray gun and the electric regulating valve for dilute ammonia water in the spray gun are connected. The free-retractable dual-fluid spray gun is connected to an induced draft fan.

2. The SNCR denitrification automatic control system as described in claim 1, characterized in that, The ammonia storage tank is equipped with an ammonia storage tank level gauge, and an ammonia pump outlet reflux electric regulating valve is installed at one end of the ammonia storage tank; one end of the ammonia pump outlet reflux electric regulating valve is connected to the ammonia storage tank, and the other end is connected to the outlet end of the ammonia delivery pump.

3. The SNCR denitrification automatic control system as described in claim 2, characterized in that, The outlet end of the ammonia water delivery pump is equipped with an ammonia water pump outlet pressure sensor, and the ammonia water pump outlet reflux electric regulating valve controls the ammonia water pump outlet pressure sensor.

4. The SNCR denitrification automatic control system as described in claim 1, characterized in that, The demineralized water tank is equipped with a demineralized water tank level gauge, and a demineralized water pump outlet reflux electric regulating valve is installed at one end of the demineralized water tank; one end of the demineralized water pump outlet reflux electric regulating valve is connected to the demineralized water tank, and the other end is connected to the outlet end of the demineralized water transfer pump.

5. The SNCR denitrification automatic control system as described in claim 4, characterized in that, The outlet end of the demineralized water transfer pump is equipped with a demineralized water pump outlet pressure sensor, and the demineralized water pump outlet reflux electric regulating valve controls the demineralized water pump outlet pressure sensor.

6. The SNCR denitrification automatic control system as described in claim 1, characterized in that, The metering and mixing system includes a metering and mixing demineralized water vortex flow meter, a metering and mixing demineralized water electric regulating valve, a metering and mixing ammonia water electromagnetic flow meter, and a metering and mixing concentrated ammonia water electric regulating valve. The metering mixed demineralized water vortex flow meter and the metering mixed demineralized water electric regulating valve are connected, and the outlet end of the metering mixed demineralized water electric regulating valve is connected to the metering mixed outlet mass flow meter; the metering mixed ammonia water electromagnetic flow meter and the metering mixed concentrated ammonia water electric regulating valve are connected.

7. The SNCR denitrification automatic control system as described in claim 1, characterized in that, The distribution injection system is connected to the outlet end of the compressed air main pipe electric regulating valve, the inlet end of the compressed air main pipe electric regulating valve is connected to the compressed air pipeline, and a compressed air main pipe pressure sensor is installed on the pipeline connecting the compressed air main pipe electric regulating valve and the distribution injection system.

8. The SNCR denitrification automatic control system as described in claim 1, characterized in that, The fire sprinkler and ammonia leak alarm system includes an ammonia leak alarm, an electric switch valve for the fire water main pipe, ammonia water storage tank sprinkler coils, and water mist nozzles. The ammonia storage tank is equipped with an ammonia leak alarm, which is electrically connected to the fire hydrant main pipe electric switch valve, which is installed on the fire hydrant pipe; both the ammonia leak alarm and the fire hydrant main pipe electric switch valve are electrically connected to the control system.

9. The SNCR denitrification automatic control system as described in claim 1, characterized in that, The control system is electrically connected to the ammonia escape online monitoring and analysis instrument.

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