A dual-control-valve-based wide flow range flow regulating system and method

Abstract

The present application relates to the technical field of gas purification, and particularly relates to a wide flow range flow regulating system and method based on double regulating valves, the system comprising a flow meter, a first regulating valve, a second regulating valve, a controller, a first analyzer and a second analyzer, the first regulating valve and the second regulating valve are both installed between an ammonia water pump and the flow meter, the flow meter is connected with a nozzle, the control ends of the first regulating valve and the second regulating valve are both connected with the controller, the flow regulating ranges of the first regulating valve and the second regulating valve partially overlap, the first analyzer is connected with a smoke inlet pipeline, the first analyzer detects the concentration of nitrogen oxides in the smoke inlet pipeline, the second analyzer is connected with a smoke outlet pipeline, the second analyzer detects the concentration of nitrogen oxides in the smoke outlet pipeline, the first analyzer and the second analyzer are both connected with the controller, and the flow meter is connected with the controller. The beneficial technical effects of the present application include: realizing wide flow range regulation of ammonia water flow, avoiding ammonia water waste and increasing of side reactions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas purification, in particular to a wide flow range flow regulating system and method based on double regulating valves. BACKGROUND

[0002] The thermal power boiler adopts SNCR+SCR coupled denitration process to remove nitrogen oxides in flue gas. The SNCR+SCR coupled denitration adopts 20% concentration of ammonia water as a reducing agent, and the flow control precision of the reducing agent directly affects the efficiency of denitration and the final nitrogen oxides emission concentration. The thermal power boiler has a large difference between night and daytime loads, especially when running at night overload, the ammonia water consumption increases significantly. The minimum consumption and the maximum consumption of ammonia water in a day differ by about twenty times. At present, a single regulating valve is used to regulate the ammonia water flow, which cannot simultaneously regulate the minimum ammonia water amount and the maximum ammonia water amount required for operation, resulting in ammonia water waste and an increase in side reactions. Therefore, it is necessary to study the flow regulating technology with a wide flow regulating range.

[0003] The prior art discloses a kind of online regulating device of small flow ammonia for denitration, comprising: intermittent ammonia supply unit, vaporization unit, buffer unit and vapor-gas mixing unit are sequentially communicated, intermittent ammonia supply unit is communicated with liquid ammonia delivery pipe, vapor-gas mixing unit is communicated with ammonia injection grid;Intermittent ammonia supply unit is used to provide quantitative liquid ammonia supply;Vaporization unit is used to vaporize liquid ammonia, vapor-gas mixing unit includes primary mixer and secondary mixer, primary mixer is used for ammonia gas dilution, and secondary mixer is used for online regulation;Adjacent two units are provided with regulating valve, and each regulating valve is electrically connected with DCS control system respectively.The technical scheme adopts intermittent ammonia supply and two-stage mixing combination, to ensure the small adjustment of ammonia flow under the condition of small ammonia consumption.But its technical scheme cannot realize the adjustment when large ammonia water flow. SUMMARY

[0004] The technical problem to be solved by the present application is that there is currently a lack of ammonia water flow regulating scheme with a wide flow regulating range. A wide flow range flow regulating system and method based on double regulating valves are proposed, which can realize wide flow regulation of ammonia water flow.

[0005] To solve the above technical problems, the present invention adopts the following technical solution: a wide flow range flow regulation system based on dual regulating valves for regulating the ammonia flow rate of an SNCR+SCR coupled denitrification device. The SNCR+SCR coupled denitrification device includes an inlet pipe, an SNCR reactor, an SCR reactor, a nozzle, an ammonia pump, and an outlet pipe. The inlet pipe, SNCR reactor, SCR reactor, and outlet pipe are connected sequentially. The nozzle is connected to the SNCR reactor. The flow regulation system includes a flow meter, a first regulating valve, a second regulating valve, a controller, and a first analyzer. The first regulating valve and the second regulating valve are both installed between the ammonia pump and the flow meter. The flow meter is connected to the nozzle. The control terminals of the first regulating valve and the second regulating valve are both connected to the controller. The flow regulation ranges of the first regulating valve and the second regulating valve partially overlap. The first analyzer is connected to the inlet pipe and detects the flue gas flow rate and nitrogen oxide concentration in the inlet pipe. The first analyzer is connected to the controller, and the flow meter is connected to the controller.

[0006] Preferably, the controller includes a flow coordination control module and an ammonia calculation module. The control terminals of the first regulating valve and the second regulating valve are both connected to the flow coordination control module. The first analyzer is connected to the ammonia calculation module. The ammonia calculation module and the flow meter are both connected to the flow coordination control module. Preferably, the flow regulation system also includes a flow buffer, which is installed between the flow meter and the SNCR reactor.

[0007] Preferably, the flow damper includes an adjusting pipe, a throat tube, a pressure plate, a spring, and a reservoir tube. The adjusting pipe connects the flow meter and the nozzle. The throat tube is connected to the adjusting pipe. The reservoir tube is open at one end and closed at the other end. The open end of the reservoir tube is connected to the throat tube. The outer wall of the pressure plate matches the shape of the inner wall of the reservoir tube. The pressure plate is movably installed inside the reservoir tube. The spring is installed between the pressure plate and the closed end of the reservoir tube.

[0008] Preferably, the flow buffer further includes a DC power supply BT and an electronic switch K1, wherein the DC power supply BT, the electronic switch K1 and the spring are connected in series, and the control terminal of the electronic switch K1 is connected to the controller.

[0009] A wide-flow-range flow regulation method based on dual regulating valves is executed by a wide-flow-range flow regulation system based on dual regulating valves as described above. The starting point of the flow regulation range of the first regulating valve in the flow regulation system is smaller than the starting point of the flow regulation range of the second regulating valve. The flow regulation method is periodically executed by the controller, and the flow regulation method includes:

[0010] The concentration of nitrogen oxides in the flue gas inlet duct is obtained by reading the detection value of the first analyzer.

[0011] The required ammonia flow rate is calculated based on the concentration of the nitrogen oxides.

[0012] The ammonia flow rate is compared with the adjustment ranges of the first regulating valve and the second regulating valve, respectively;

[0013] If the ammonia flow rate falls within the adjustment range of the first regulating valve, the controller closes the second regulating valve and sets the opening of the first regulating valve to match the ammonia flow rate.

[0014] If the ammonia flow rate falls within the adjustment range of the second regulating valve, the controller closes the first regulating valve and sets the opening of the second regulating valve to match the ammonia flow rate.

[0015] If the ammonia flow rate falls within the overlapping range of the adjustment range of the first regulating valve and the adjustment range of the second regulating valve, then calculate the difference between the ammonia flow rate and the end point of the adjustment range of the first regulating valve, and record it as the first difference; calculate the difference between the ammonia flow rate and the start point of the adjustment range of the second regulating valve, and record it as the second difference.

[0016] If the first difference is greater than the second difference, the controller closes the second regulating valve and sets the opening of the first regulating valve so that the opening of the first regulating valve matches the ammonia flow rate.

[0017] If the first difference is not greater than the second difference, the controller closes the first regulating valve and sets the opening of the second regulating valve to match the ammonia flow rate. Preferably, a day is divided into 24 cycles of 1 hour, and the controller executes the flow regulation method in 1-hour cycles.

[0018] Preferably, before the start of the first cycle each day, the controller calculates the historical average ammonia flow rate for each cycle. After calculating the required ammonia flow rate for the current cycle based on the concentration of nitrogen oxides, the controller reads the historical average ammonia flow rate for the next cycle.

[0019] If the historical average ammonia flow rate of the next cycle is greater than the ammonia flow rate required for the current cycle, and the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle exceeds the preset first threshold, then after calculating the first difference, the first difference is divided by 2 to obtain the final value of the first difference.

[0020] If the historical average ammonia flow rate of the next cycle is less than the ammonia flow rate required for the current cycle, and the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle exceeds the preset first threshold, then after calculating the second difference, the second difference is divided by 2 to obtain the final value of the second difference.

[0021] Preferably, the controller calculates the historical average ammonia flow rate for each cycle, and after calculating the nitrogen oxide concentration to obtain the ammonia flow rate required for the current cycle, it reads the historical average ammonia flow rate for the next cycle.

[0022] The method by which the controller controls the flow buffer includes:

[0023] If the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required in the current cycle exceeds a preset second threshold, the controller will control the duty cycle of the electronic switch K1 to the first duty cycle.

[0024] If the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle does not exceed the preset second threshold, the controller will control the duty cycle of the electronic switch K1 to the second duty cycle, where the first duty cycle is less than the second duty cycle.

[0025] Preferably, the controller collects the detection value of the flow meter at a preset frequency and records it as the real-time detection value of ammonia flow. It calculates the variance of the real-time detection value of ammonia flow collected within a preset time period. If the variance exceeds a preset variance threshold, the controller increases the duty cycle of the electronic switch K1. Conversely, if the variance does not exceed the preset variance threshold, the controller decreases the duty cycle of the electronic switch K1.

[0026] The beneficial technical effects of this invention include: the dual-regulating valve flow regulation system, composed of a first regulating valve and a second regulating valve, enables wide-range regulation of ammonia flow rate, matching the ammonia demand of the thermal power boiler under different loads, and avoiding ammonia waste and increased side reactions; the flow coordination control module and the ammonia calculation module respectively complete the control of the regulating valves and the calculation of ammonia demand, making the control process more reliable and stable; and the flow buffer reduces flow fluctuations during ammonia supply, which helps to more accurately control the amount of ammonia supplied.

[0027] Other features and advantages of the present invention will be disclosed in detail in the following detailed description and accompanying drawings. Attached Figure Description

[0028] The invention will be further described below with reference to the accompanying drawings:

[0029] Figure 1This is a schematic diagram of the flow regulation system structure according to an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the flow buffer structure according to an embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram of the flow regulation method according to an embodiment of the present invention.

[0032] Figure 4 This is a schematic diagram of the flow buffer control method according to an embodiment of the present invention.

[0033] The components are as follows: 1. Smoke inlet pipe; 2. First analyzer; 3. SNCR reactor; 4. Nozzle; 5. Flow buffer; 6. Flow meter; 7. First regulating valve; 8. Second regulating valve; 9. SCR reactor; 10. Flow coordination control module; 11. Ammonia calculation module; 12. Ammonia pump; 13. Second analyzer; 14. Controller; 15. Smoke outlet pipe; 51. Regulating pipe; 52. Throat tube; 53. Pressure plate; 54. Spring; 55. Liquid storage pipe. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be explained and described below with reference to the accompanying drawings. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present invention.

[0035] In the following description, terms such as “inner,” “outer,” “upper,” “lower,” “left,” and “right” are used only to indicate orientation or positional relationship for the convenience of describing the embodiments and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0036] Before introducing the technical solution of this embodiment, the application scenario of this embodiment will be introduced.

[0037] SNCR, short for Selective Non-Catalytic Reduction, refers to the process of reducing nitrogen oxides in flue gas to harmless nitrogen and water by injecting a reducing agent within a suitable "temperature window" for denitrification reactions, without the aid of a catalyst. This technology typically uses in-furnace injection of ammonia, urea, or hydrocyanic acid as the reducing agent to reduce NOx. The reducing agent only reacts with NOx in the flue gas and generally does not react with oxygen. Because this technology does not use a catalyst, it is called Selective Non-Catalytic Reduction (SNCR). Since this process does not use a catalyst, a reducing agent must be added in a high-temperature zone. The reducing agent is injected into the furnace at a temperature of 850~1100℃, where it rapidly decomposes into NH3, which reacts with NOx in the flue gas to produce N2 and water. SNCR is commonly used in boiler furnaces to reduce NOx emissions to approximately 200 mg / Nm3. Based on the preparation, dilution, injection, and control system of the reducing agent in an in-furnace SNCR system, a flue gas denitrification device (SCR) is added to form an SNCR / SCR combined denitrification process.

[0038] SCR (Selective Catalytic Reduction) is a method that improves the selectivity of N2 under catalysis, thereby reducing the consumption of NH3. The principle of SCR is that, under the action of a catalyst, the reducing agent NH3 selectively reduces NO and NO2 to N2 at 290-400℃, while almost no oxidation reaction occurs between NH3 and O2, thus improving the selectivity of N2 and reducing the consumption of NH3. The main reactions are as follows: 4NH3 + 4NO + O2 = 4N2 + 6H2O, 8NH3 + 6NO2 = 7N2 + 12H2O, 4NH3 + 3O2 = 2N2 + 6H2O, 4NH3 + 5O2 = 4NO + 6H2O, and 2NH3 reversibly generates N2 + 3H2. The use of a catalyst in SCR significantly lowers the reaction temperature, allowing the reduction reaction to proceed at lower temperatures. At a molar ratio of NH3 / NOx of 1, the NOx removal rate can reach 90%.

[0039] In the SNCR+SCR coupled denitrification process, ammonia is used as a reducing agent. To ensure denitrification efficiency, the ammonia flow rate needs to be matched with the volume of flue gas to be denitrated. The volume of flue gas to be denitrated is determined by the load of the thermal power boiler, which in turn is determined by the user load. Throughout the day, the user load exhibits significant peaks and troughs, with a difference of approximately twenty times between the peaks and troughs. This results in a large difference between the minimum and maximum ammonia flow rates required for the SNCR+SCR coupled denitrification process, exceeding the flow regulation range of conventional control valves. When the required ammonia flow rate is less than the minimum regulating flow rate of the control valve, it leads to an oversupply of ammonia, causing ammonia waste and increased side reactions. Therefore, this embodiment proposes a wide-range flow regulation system based on dual regulating valves for regulating the ammonia flow rate in an SNCR+SCR coupled denitrification device. The SNCR+SCR coupled denitrification device includes an inlet pipe 1, an SNCR reactor 3, an SCR reactor 9, a nozzle 4, an ammonia pump 12, and an outlet pipe 15. The inlet pipe 1, SNCR reactor 3, SCR reactor 9, and outlet pipe 15 are sequentially connected, and the nozzle 4 is connected to the SNCR reactor 3. Please refer to the appendix. Figure 1 The flow regulation system includes a flow meter 6, a first regulating valve 7, a second regulating valve 8, a controller 14, and a first analyzer 2. The first regulating valve 7 and the second regulating valve 8 are both installed between the ammonia pump 12 and the flow meter 6. The flow meter 6 is connected to the nozzle 4. The control terminals of the first regulating valve 7 and the second regulating valve 8 are both connected to the controller 14. The flow regulation ranges of the first regulating valve 7 and the second regulating valve 8 partially overlap. The first analyzer 2 is connected to the flue gas inlet pipe 1. The first analyzer 2 detects the flue gas flow rate and nitrogen oxide concentration in the flue gas inlet pipe 1. The first analyzer 2 is connected to the controller 14. The flow meter 6 is connected to the controller 14.

[0040] On the other hand, in this embodiment, the controller 14 includes a flow coordination control module 10 and an ammonia calculation module 11. The control terminals of the first regulating valve 7 and the second regulating valve 8 are both connected to the flow coordination control module 10, the first analyzer 2 is connected to the ammonia calculation module 11, and both the ammonia calculation module 11 and the flow meter 6 are connected to the flow coordination control module 10. The flow coordination control module 10 and the ammonia calculation module 11 respectively control the regulating valves and calculate the ammonia demand, making the control process more reliable and stable.

[0041] The ammonia calculation module 11 calculates the required ammonia flow rate based on the flue gas flow rate and nitrogen oxide concentration obtained from the first analyzer 2, according to the SNCR process ratio and the NH3 concentration in the ammonia solution. Then, based on the flow rate adjustment ranges of the first regulating valve 7 and the second regulating valve 8, it selects one of them for flow rate adjustment. If the required ammonia flow rate is large, the second regulating valve 8 is used and the first regulating valve 7 is closed; if the ammonia flow rate is small, the first regulating valve 7 is used and the second regulating valve 8 is closed. The flow rate adjustment ranges of the first regulating valve 7 and the second regulating valve 8 overlap; when the required ammonia flow rate falls within this overlap, either valve can be selected for adjustment.

[0042] On the other hand, in this embodiment, the flow regulation system also includes a second analyzer 13, which is connected to the flue gas outlet pipe 15 to detect the flue gas flow rate and nitrogen oxide concentration in the flue gas outlet pipe 15. The second analyzer 13 is also connected to the ammonia calculation module 11. The concentration of nitrogen oxides in the flue gas outlet pipe 15 is obtained through the second analyzer 13 to obtain the final denitrification rate. When the denitrification rate decreases, the ammonia supply is increased by a preset amount. When the denitrification rate reaches the target, the ammonia supply is reduced by a preset amount.

[0043] On the other hand, the flow regulation system in this embodiment also includes a flow buffer 5, which is installed between the flow meter 6 and the SNCR reactor 3.

[0044] This embodiment provides the specific structure of the flow buffer 5. Please refer to the appendix. Figure 2 The flow buffer 5 includes an adjusting pipe 51, a throat tube 52, a pressure plate 53, a spring 54, and a storage tube 55. The adjusting pipe 51 connects the flow meter 6 and the nozzle 4. The throat tube 52 connects to the adjusting pipe 51. The storage tube 55 is open at one end and closed at the other, with the open end connected to the throat tube 52. The outer wall of the pressure plate 53 matches the inner wall of the storage tube 55, and the pressure plate 53 is movably installed inside the storage tube 55. The spring 54 is installed between the pressure plate 53 and the closed end of the storage tube 55. Due to the elasticity of the spring 54, when the ammonia flow rate in the adjusting pipe 51 increases, the spring 54 is compressed, and some of the ammonia in the adjusting pipe 51 will pass through the throat tube 52 into the storage tube 55, reducing the ammonia flow rate in the adjusting pipe 51. When the ammonia flow rate in the adjusting pipe 51 decreases, the spring 54 extends, and some of the ammonia in the storage tube 55 will pass through the throat tube 52 into the adjusting pipe 51, increasing the ammonia flow rate in the adjusting pipe 51.

[0045] The flow buffer 5 also includes a DC power supply BT and an electronic switch K1. The DC power supply BT, electronic switch K1, and spring 54 are connected in series, and the control terminal of electronic switch K1 is connected to controller 14. By controlling the duty cycle of electronic switch K1, the current in spring 54 can be adjusted. Changes in the current in spring 54 will cause changes in the spring's elastic coefficient. When the duty cycle of electronic switch K1 is increased, the current in spring 54 increases, and the spring's elastic coefficient decreases, making it more effective in balancing changes in ammonia flow rate in regulating pipe 51. When the duty cycle of electronic switch K1 is decreased, the current in spring 54 decreases, and the spring's elastic coefficient increases, allowing changes in ammonia pressure in regulating pipe 51 to more quickly follow the flow rate adjustment by the first regulating valve 7 or the second regulating valve 8.

[0046] On the other hand, this embodiment provides a wide flow range flow regulation method based on dual regulating valves, executed by a wide flow range flow regulation system based on dual regulating valves as described above. The starting point of the flow regulation range of the first regulating valve 7 in the flow regulation system is smaller than the starting point of the flow regulation range of the second regulating valve 8. The flow regulation method is executed periodically by the controller 14. Please refer to the appendix. Figure 3 Flow regulation methods include:

[0047] Step A01) Read the detection value of the first analyzer 2 to obtain the concentration of nitrogen oxides in the flue gas inlet duct 1;

[0048] Step A02) Calculate the required ammonia flow rate based on the concentration of nitrogen oxides;

[0049] Step A03) Compare the ammonia flow rate with the adjustment ranges of the first regulating valve 7 and the second regulating valve 8 respectively;

[0050] Step A04) If the ammonia flow rate falls within the adjustment range of the first regulating valve 7, the controller 14 closes the second regulating valve 8 and sets the opening of the first regulating valve 7 so that the opening of the first regulating valve 7 matches the ammonia flow rate.

[0051] Step A05) If the ammonia flow rate falls within the adjustment range of the second regulating valve 8, the controller 14 closes the first regulating valve 7 and sets the opening of the second regulating valve 8 so that the opening of the second regulating valve 8 matches the ammonia flow rate.

[0052] Step A06) If the ammonia flow rate falls within the overlapping range of the adjustment range of the first regulating valve 7 and the second regulating valve 8, calculate the difference between the ammonia flow rate and the end point of the adjustment range of the first regulating valve 7, and record it as the first difference. Calculate the difference between the ammonia flow rate and the start point of the adjustment range of the second regulating valve 8, and record it as the second difference.

[0053] Step A07) If the first difference is greater than the second difference, the controller 14 closes the second regulating valve 8 and sets the opening of the first regulating valve 7 so that the opening of the first regulating valve 7 matches the ammonia flow rate.

[0054] (Step A08) If the first difference is not greater than the second difference, the controller 14 closes the first regulating valve 7 and sets the opening of the second regulating valve 8 to match the ammonia flow rate. The day is divided into 24 cycles of one hour each, and the controller 14 executes the flow regulation method in one-hour cycles. Through the dual-regulating valve flow regulation system composed of the first regulating valve 7 and the second regulating valve 8, a wide flow range of ammonia flow rate regulation is achieved, matching the ammonia demand of the thermal power boiler under different loads, and avoiding ammonia waste and increased side reactions.

[0055] Before the start of the first cycle each day, controller 14 calculates the historical average ammonia flow rate for each cycle. After calculating the ammonia flow rate required for the current cycle based on the concentration of nitrogen oxides, controller 14 reads the historical average ammonia flow rate for the next cycle.

[0056] If the historical average ammonia flow rate of the next cycle is greater than the ammonia flow rate required for the current cycle, and the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle exceeds the preset first threshold, then after calculating the first difference, the first difference is divided by 2 to obtain the final value of the first difference.

[0057] If the historical average ammonia flow rate of the next cycle is less than the ammonia flow rate required for the current cycle, and the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle exceeds the preset first threshold, then after calculating the second difference, the second difference is divided by 2 to obtain the final value of the second difference.

[0058] By using the historical average ammonia flow rate for the next cycle as a prediction of ammonia flow rate changes, if the required ammonia flow rate is about to increase, and the required ammonia flow rate falls within the overlapping range of the flow regulation ranges of the first regulating valve 7 and the second regulating valve 8, the valve will be switched from the first regulating valve 7 to the second regulating valve 8 for regulation earlier. Conversely, if the required ammonia flow rate is about to decrease, and the required ammonia flow rate falls within the overlapping range of the flow regulation ranges of the first regulating valve 7 and the second regulating valve 8, the valve will be switched from the second regulating valve 8 to the first regulating valve 7 for regulation earlier.

[0059] Please see the appendix Figure 4 The method by which controller 14 controls flow buffer 5 includes:

[0060] Step B01) Controller 14 calculates the historical average ammonia flow rate for each cycle and the concentration of nitrogen oxides. After obtaining the ammonia flow rate required for the current cycle, it reads the historical average ammonia flow rate for the next cycle.

[0061] Step B02) If the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required in the current cycle exceeds the preset second threshold, the controller 14 will control the duty cycle of the electronic switch K1 to the first duty cycle.

[0062] Step B03) If the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle does not exceed the preset second threshold, then the controller 14 controls the duty cycle of the electronic switch K1 to the second duty cycle, where the first duty cycle is less than the second duty cycle.

[0063] The controller 14 collects the detection value of the flow meter 6 at a preset frequency and records it as the real-time detection value of ammonia flow. It calculates the variance of the real-time detection value of ammonia flow collected within a preset time period. If the variance exceeds the preset variance threshold, the controller 14 increases the duty cycle of the electronic switch K1. Conversely, if the variance does not exceed the preset variance threshold, the controller 14 decreases the duty cycle of the electronic switch K1.

[0064] When the required ammonia flow rate remains essentially constant, the duty cycle of electronic switch K1 is increased to balance the changes in ammonia flow rate caused by fluctuations in the operation of ammonia pump 12. When the required ammonia flow rate changes significantly, the duty cycle of electronic switch K1 is decreased so that the ammonia flow rate can more quickly follow the flow rate adjustment of the first regulating valve 7 or the second regulating valve 8.

[0065] By using the flow buffer 5 to reduce flow fluctuations during the ammonia supply process, it is possible to more accurately control the amount of ammonia supplied.

[0066] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A wide-range flow regulation system based on dual regulating valves for regulating ammonia flow in an SNCR+SCR coupled denitrification device, wherein the SNCR+SCR coupled denitrification device includes an inlet pipe, an SNCR reactor, an SCR reactor, a nozzle, an ammonia pump, and an outlet pipe, wherein the inlet pipe, the SNCR reactor, the SCR reactor, and the outlet pipe are sequentially connected, and the nozzle is connected to the SNCR reactor, characterized in that, The flow regulation system includes a flow meter, a first regulating valve, a second regulating valve, a controller, and a first analyzer. The first regulating valve and the second regulating valve are both installed between the ammonia pump and the flow meter. The flow meter is connected to a nozzle. The control terminals of the first regulating valve and the second regulating valve are both connected to the controller. The flow regulation ranges of the first regulating valve and the second regulating valve partially overlap. The first analyzer is connected to the flue gas inlet pipe and detects the flue gas flow rate and nitrogen oxide concentration in the flue gas inlet pipe. The first analyzer is connected to the controller, and the flow meter is connected to the controller. The flow regulation system also includes a flow buffer installed between the flow meter and the SNCR reactor; The flow damper includes an adjusting pipe, a throat tube, a pressure plate, a spring, and a liquid storage tube. The adjusting pipe connects the flow meter and the nozzle. The throat tube is connected to the adjusting pipe. The liquid storage tube is open at one end and closed at the other end. The open end of the liquid storage tube is connected to the throat tube. The outer wall of the pressure plate matches the shape of the inner wall of the liquid storage tube. The pressure plate is movably installed inside the liquid storage tube. The spring is installed between the pressure plate and the closed end of the liquid storage tube. The flow buffer also includes a DC power supply BT and an electronic switch K1. The DC power supply BT, the electronic switch K1 and the spring are connected in series, and the control terminal of the electronic switch K1 is connected to the controller.

2. The wide flow range flow regulation system based on dual regulating valves according to claim 1, characterized in that, The controller includes a flow coordination control module and an ammonia calculation module. The control terminals of the first regulating valve and the second regulating valve are both connected to the flow coordination control module. The first analyzer is connected to the ammonia calculation module. The ammonia calculation module and the flow meter are both connected to the flow coordination control module.

3. A wide flow range flow regulation method based on dual regulating valves, executed by a wide flow range flow regulation system based on dual regulating valves as described in any one of claims 1 to 2, wherein the starting point of the flow regulation range of the first regulating valve in the flow regulation system is smaller than the starting point of the flow regulation range of the second regulating valve, characterized in that, The flow regulation method is executed periodically by the controller, and the flow regulation method includes: The concentration of nitrogen oxides in the flue gas inlet duct is obtained by reading the detection value of the first analyzer. The required ammonia flow rate is calculated based on the concentration of the nitrogen oxides. The ammonia flow rate is compared with the adjustment ranges of the first regulating valve and the second regulating valve, respectively; If the ammonia flow rate falls within the adjustment range of the first regulating valve, the controller closes the second regulating valve and sets the opening of the first regulating valve to match the ammonia flow rate. If the ammonia flow rate falls within the adjustment range of the second regulating valve, the controller closes the first regulating valve and sets the opening of the second regulating valve to match the ammonia flow rate. If the ammonia flow rate falls within the overlapping range of the adjustment range of the first regulating valve and the adjustment range of the second regulating valve, then calculate the difference between the ammonia flow rate and the end point of the adjustment range of the first regulating valve, and record it as the first difference; calculate the difference between the ammonia flow rate and the start point of the adjustment range of the second regulating valve, and record it as the second difference. If the first difference is greater than the second difference, the controller closes the second regulating valve and sets the opening of the first regulating valve so that the opening of the first regulating valve matches the ammonia flow rate. If the first difference is not greater than the second difference, the controller closes the first regulating valve and sets the opening of the second regulating valve so that the opening of the second regulating valve matches the ammonia flow rate.

4. The wide flow range flow regulation method based on dual regulating valves according to claim 3, characterized in that, The day is divided into 24 cycles of 1 hour each, and the controller executes the flow regulation method in 1-hour cycles.

5. A wide flow range flow regulation method based on dual regulating valves according to claim 4, characterized in that, Before the start of the first cycle each day, the controller calculates the historical average ammonia flow rate for each cycle. After calculating the ammonia flow rate required for the current cycle based on the concentration of nitrogen oxides, the controller reads the historical average ammonia flow rate for the next cycle. If the historical average ammonia flow rate of the next cycle is greater than the ammonia flow rate required for the current cycle, and the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle exceeds the preset first threshold, then after calculating the first difference, the first difference is divided by 2 to obtain the final value of the first difference. If the historical average ammonia flow rate of the next cycle is less than the ammonia flow rate required for the current cycle, and the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle exceeds the preset first threshold, then after calculating the second difference, the second difference is divided by 2 to obtain the final value of the second difference.

6. The wide flow range flow regulation method based on dual regulating valves according to claim 4, characterized in that, The controller calculates the historical average ammonia flow rate for each cycle. After calculating the nitrogen oxide concentration to obtain the ammonia flow rate required for the current cycle, it reads the historical average ammonia flow rate for the next cycle. The method by which the controller controls the flow buffer includes: If the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required in the current cycle exceeds a preset second threshold, the controller will control the duty cycle of the electronic switch K1 to the first duty cycle. If the absolute value of the difference between the historical average ammonia flow rate of the next cycle and the ammonia flow rate required for the current cycle does not exceed the preset second threshold, the controller will control the duty cycle of the electronic switch K1 to the second duty cycle, where the first duty cycle is less than the second duty cycle.

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