Method for controlling addition of ammonia to boiler feed water during condensate water flow rate change

Abstract

The present application relates to a method for controlling addition of ammonia to boiler feed water during condensate water flow rate change. The method is based on a system for adding ammonia to boiler feed water. Said system comprises a condenser, a condensate water pipe, an ammonia liquid pipe, an ammonia liquid metering tank and a water feeding pipe. A condensate water pump is arranged on the condensate water pipe. A second metering pump is arranged on the ammonia liquid pipe, and the second metering pump is a variable frequency pump. The method for controlling addition of ammonia to boiler feed water during condensate water flow rate change comprises the following steps: S1, preparing, in an ammonia liquid metering tank, an ammonia solution having an ammonia concentration of Cmetering tank NH3, and determining a flow rate change value q of a second metering pump under each Hz frequency change; S2, determining a change value ∆Qcondensate water of the flow rate of condensate water in a condensate water pipe, and determining that the condensate water in the condensate water pipe reaches the required ammonia concentration change value ∆CNH3 meeting water feeding requirements; and S3, adjusting the frequency of the second metering pump. Therefore, the method for controlling addition of ammonia to boiler feed water during condensate water flow rate change in the present application has the advantage of being convenient for real-time and accurate adjustment of the pH value of feed water.

Description

A method for controlling ammonia addition to boiler feed water when condensate flow rate fluctuates

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to a Chinese patent application filed with the Patent Office of China on March 29, 2024, with application number 202410378082.7 and invention name “A method for controlling the addition of ammonia to boiler feed water when the condensate flow rate changes”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the technical field of boiler feed water, and in particular to a method for controlling the addition of ammonia to boiler feed water when the condensate flow rate varies. Background Art

[0004] Boiler feedwater pH control is a crucial component of a power plant's chemical system. Increasing the feedwater's pH by adding ammonia to the feedwater pipeline is the most economical and practical way to prevent metal corrosion. In related technologies, the condensate flow rate from the condenser fluctuates with boiler load fluctuations. If the amount of ammonia added to the incremental condensate is not adjusted promptly and accurately, the pH of the boiler feedwater will not reach the set value, becoming unstable and failing to meet feedwater requirements.

[0005] Summary of the Invention

[0006] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, an embodiment of the present application provides a method for controlling the addition of ammonia to boiler feed water when the condensate flow rate varies.

[0007] The boiler feed water ammonia addition control method when the condensate flow rate changes in the embodiment of the present application is based on a boiler feed water ammonia addition system, which includes a condenser, a condensate pipeline, an ammonia liquid pipeline, an ammonia liquid metering tank and a feed water pipeline. The outlet of the condenser is connected to the inlet of the feed water pipeline through the condensate pipeline, the outlet of the ammonia liquid metering tank is connected to the inlet of the feed water pipeline through the ammonia liquid pipeline, and the outlet of the feed water pipeline is connected to the water inlet of the boiler. A condensate pump is provided on the condensate pipeline, and a second metering pump is provided on the ammonia liquid pipeline. The second metering pump is a variable frequency pump.

[0008] The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate changes comprises the following steps:

[0009] S1, configure the ammonia concentration in the ammonia liquid metering tank to be C 计 NH3 ammonia solution, determining the flow rate change value q of the second metering pump under each Hz frequency change;

[0010] S2. Determine the change value ΔQ of the flow rate of the condensate in the condensate pipeline凝 , determine the ammonia concentration change value △C required for the condensate in the condensate pipeline to meet the water supply requirements NH3 ;

[0011] S3. Adjust the frequency of the second metering pump so that the ammonia concentration in the water in the water supply pipeline meets the water supply requirements, and the frequency adjustment value f of the second metering pump satisfies the following first formula:

[0012] In the first formula: f is the frequency adjustment value of the second metering pump, △C NH3 The ammonia concentration change value required for the condensate in the condensate pipeline to meet the water supply requirements, △Q 凝 is the change in the flow rate of the condensate in the condensate pipeline, q is the change in the flow rate of the second metering pump per Hz frequency change, C 计 NH3 is the ammonia concentration value of the ammonia solution in the ammonia liquid metering tank.

[0013] Therefore, the boiler feed water ammonia addition control method according to the present application when the condensate flow rate changes has the advantage of facilitating real-time and accurate adjustment of the pH value of the feed water.

[0014] In some embodiments, a first ammonia concentration monitor is provided on the condensate pipeline;

[0015] In step S1, the ammonia concentration that meets the water supply requirement is C 给 NH3 ;

[0016] In step S2, the ammonia concentration of the condensed water in the condensed water pipeline is monitored by the first ammonia concentration monitor and the ammonia concentration is C 凝 NH3 , wherein the condensate in the condensate pipeline reaches the required ammonia concentration change value △C to meet the water supply requirements NH3 Satisfies the following second formula: △C NH3 =C 给 NH3 -C 凝 NH3

[0017] In the second formula: △C NH3 The ammonia concentration change value required for the condensate in the condensate pipeline to meet the water supply requirements, C 凝 NH3 To monitor the ammonia concentration of the condensate in the condensate pipeline using the first ammonia concentration monitor, C 给 NH3 It is the ammonia concentration value of the water in the water supply pipeline that meets the water supply requirements.

[0018] In some embodiments, the ammonia liquid metering tank is provided with a second ammonia concentration monitor;

[0019] In step S1, the second ammonia concentration monitor is used to monitor the ammonia concentration of the ammonia solution in the ammonia liquid metering tank, so as to configure the ammonia concentration in the ammonia liquid metering tank to be C 计 NH3 of ammonia solution.

[0020] In some embodiments, a third ammonia concentration monitor is provided on the water supply pipeline;

[0021] The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate changes includes:

[0022] S4, using the third ammonia concentration monitor to monitor the ammonia concentration value C of the water in the water supply pipeline 测 NH3 If the ammonia concentration value C monitored by the third ammonia concentration monitor is 测 NH3 The required value C of ammonia concentration in the water supply pipe 给 NH3 If the difference between the two values ​​is within a first preset range, it is determined that the ammonia concentration in the water supply in the water supply pipeline meets the water supply requirement;

[0023] S5. Utilize the monitoring data of the third ammonia concentration monitor to obtain the pH value of the feed water in the water supply pipeline.

[0024] In some embodiments, the first ammonia concentration monitor, the second ammonia concentration monitor, and the third ammonia concentration monitor are all conductivity meters;

[0025] The first ammonia concentration monitor is used to monitor the conductivity of the condensed water in the condensed water pipeline, and can determine the ammonia concentration of the condensed water in the condensed water pipeline according to the conductivity of the condensed water in the condensed water pipeline;

[0026] The second ammonia concentration monitor is used to monitor the conductivity of the ammonia solution in the ammonia liquid metering tank, and can determine the ammonia concentration of the ammonia solution in the ammonia liquid metering tank according to the conductivity of the ammonia solution in the ammonia liquid metering tank;

[0027] The third ammonia concentration monitor is used to monitor the conductivity of the feed water in the water supply pipeline, and can determine the ammonia concentration of the feed water in the water supply pipeline according to the conductivity of the feed water in the water supply pipeline;

[0028] The ammonia concentration value and the conductivity value SC in the liquid satisfy the following third formula: C NH3 =(13.2×SC 2 +62.7×SC)×10 -3

[0029] In the third formula: C NH3 is the ammonia concentration in the liquid, and SC is the conductivity of the liquid monitored by the conductivity meter.

[0030] In some embodiments, the frequency adjustment value f of the second metering pump is calculated using the following formula:

[0031] The fourth formula: △C NH3 ×△Q 凝 =△Q 计 ×C 计 NH3

[0032] Fifth formula: f=△Q 计 ÷q

[0033] In the fourth and fifth formulas: △Q 计 is the discharge flow rate change value of the second metering pump.

[0034] In some embodiments, a first flow meter is provided on the condensate pipeline;

[0035] In step S2, the first flow meter is used to monitor the change value ΔQ of the flow of the condensate in the condensate pipeline. 凝 ;

[0036] A second flow meter is provided on the ammonia liquid pipeline;

[0037] In step S2, the second flow meter is used to monitor the change value ΔQ of the flow rate of the ammonia solution in the ammonia solution pipeline. 计 .

[0038] In some embodiments, the boiler feed water ammonia addition system includes

[0039] a deaerator, wherein the inlet of the deaerator is connected to the outlet of the water supply pipeline;

[0040] A fourth pipeline, the inlet of the fourth pipeline is connected to the outlet of the deaerator, a third pump body is provided on the fourth pipeline, and the outlet of the fourth pipeline is connected to the water inlet of the boiler.

[0041] In some embodiments, the boiler feed water ammonia addition system includes

[0042] a first heater, the first heater being arranged on the water supply pipeline;

[0043] A second heater is provided on the fourth pipeline.

[0044] In some embodiments, the condensate pipeline includes a first branch and a second branch connected in parallel, the first branch is provided with a valve, and the second branch is provided with a fine treatment device. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG1 is a schematic diagram of a boiler feed water ammonia addition system according to an embodiment of the present application.

[0046] Figure numerals: 1. Condensate pipeline, 2. Condensate pipeline, 3. Ammonia liquid metering tank, 4. Ammonia liquid pipeline, 5. Feed water pipeline, 6. Fourth pipeline, 7. Condensate pump, 8. Second metering pump, 9. Third pump body, 10. First ammonia concentration monitor, 11. Second ammonia concentration monitor, 12. Third ammonia concentration monitor, 13. First flow meter, 14. Second flow meter, 15. Deaerator, 16. First heater, 17. First branch, 18. Second branch, 19. Valve, 20. Fine treatment device, 21. Second heater, 22. Boiler. DETAILED DESCRIPTION

[0047] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present application, but should not be understood as limiting the present application.

[0048] The following describes a method for controlling boiler feed water ammonia addition when condensate flow varies according to an embodiment of the present application with reference to the accompanying drawings. As shown in FIG1 , a method for controlling boiler feed water ammonia addition when condensate flow varies according to an embodiment of the present application is based on a boiler feed water ammonia addition system.

[0049] The boiler feed water ammonia addition system includes a condenser 1, a condensate pipeline 2, an ammonia liquid pipeline 4, an ammonia liquid metering tank 3, a feed water pipeline 5, a deaerator 15, a fourth pipeline 6, a first heater 16 and a second heater 21.

[0050] The outlet of the condenser 1 is connected to the inlet of the water supply pipeline 5 through the condensate pipeline 2. A condensate pump 7 is provided on the condensate pipeline 2 so that the condensate discharged from the condenser 1 can flow into the water supply pipeline 5.

[0051] The outlet of the ammonia liquid metering tank 3 is connected to the inlet of the water supply line 5 via the ammonia liquid pipeline 4. A second metering pump 8 is provided on the ammonia liquid pipeline 4. This second metering pump 8 is a variable frequency pump, and its discharge flow rate can be varied by adjusting its frequency. This allows the ammonia solution within the ammonia liquid metering tank 3 to flow into the water supply line 5, thereby adjusting the ammonia concentration of the feed water therein and, consequently, the pH value of the feed water to the boiler 22. The outlet of the water supply line 5 is connected to the water inlet of the boiler 22. The discharge flow rate of the second metering pump 8 (variable frequency pump) is positively correlated with the operating frequency, and adjustment is relatively convenient and precise, allowing for accurate regulation of the ammonia concentration and, consequently, the pH value of the feed water in the water supply line 5.

[0052] The inlet of deaerator 15 is connected to the outlet of feedwater line 5. The inlet of fourth line 6 is connected to the outlet of deaerator 15. A third pump body 9 is mounted on fourth line 6, and the outlet of fourth line 6 is connected to the water inlet of boiler 22. This allows feedwater discharged from feedwater line 5 to pass through deaerator 15 to remove oxygen, and then pass through fourth line 6 to boiler 22.

[0053] The first heater 16 is provided on the water supply pipeline 5, and the second heater 21 is provided on the fourth pipeline 6. Specifically, the first heater 16 is a low-pressure heater, and the second heater 21 is a high-pressure heater.

[0054] As shown in Figure 1, the condensate pipeline 2 includes a first branch 17 and a second branch 18 connected in parallel. A valve 19 is provided on the first branch 17, and a polishing device 20 is provided on the second branch 18. Therefore, when the valve 19 closes the first branch 17, the condensate can flow through the second branch 18 into the polishing device 20 to remove impurities in the condensate.

[0055] Therefore, the boiler feed water ammonia addition system according to the present application has the advantage of facilitating real-time and accurate adjustment of the pH value of the feed water.

[0056] According to the present application, a method for controlling the addition of ammonia to boiler feed water when the condensate flow rate varies includes the following steps.

[0057] S1, configure the ammonia concentration in the ammonia liquid metering tank 3 to C 计 NH3 The flow rate change value q of the second metering pump 8 per Hz frequency change is determined. Specifically, the output (flow rate) of the second metering pump 8 per Hz frequency change at a fixed stroke can be obtained through experiments.

[0058] In some embodiments, a second ammonia concentration monitor 11 is provided on the ammonia liquid metering tank 3 .

[0059] In step S1, the second ammonia concentration monitor 11 is used to monitor the ammonia concentration of the ammonia solution in the ammonia liquid metering tank 3, so as to configure the ammonia concentration in the ammonia liquid metering tank 3 to be C计 NH3 Specifically, the ammonia concentration of the ammonia solution in the ammonia liquid metering tank 3 can be adjusted according to the value monitored by the second ammonia concentration monitor 11, so that the ammonia concentration of the ammonia solution in the ammonia liquid metering tank 3 is C 计 NH3 .

[0060] In step S1, the ammonia concentration that meets the water supply requirements is C 给 NH3 Specifically, according to the pH value required for water supply, set the ammonia concentration value C that meets the water supply requirement (pH value) 给 NH3 .

[0061] S2. Determine the change in the flow rate of condensate in condensate pipe 2, △Q 凝 , determine the ammonia concentration change value △C required for the condensate in condensate line 2 to meet the water supply requirements (pH value) NH3 .

[0062] In some embodiments, a first ammonia concentration monitor 10 is provided on the condensate pipe 2. In step S2, the ammonia concentration of the condensate in the condensate pipe 2 is monitored by the first ammonia concentration monitor 10. 凝 NH3 .

[0063] The condensate in the condensate pipe 2 reaches the required ammonia concentration change value △C to meet the water supply requirements (pH value). NH3 Satisfies the following second formula: △C NH3 =C 给 NH3 -C 凝 NH3 In the second formula: △C NH3 (mg / L) The condensate in the condensate pipe 2 reaches the required ammonia concentration change value to meet the water supply requirements, C 凝 NH3 (mg / L) is the ammonia concentration value of the condensate in the condensate pipeline 2 monitored by the first ammonia concentration monitor 10, C 给 NH3 (mg / L) is the ammonia concentration value of the feed water in the feed water pipeline 5 that meets the feed water requirements (pH value). That is, by monitoring the ammonia concentration value C of the condensate in the condensate pipeline 2 凝 NH3 Calculate the ammonia concentration change △C required for the condensate in condensate line 2 to meet the water supply requirements NH3 .

[0064] S3. The frequency of the second metering pump 8 is adjusted so that the ammonia concentration in the water in the water supply pipeline 5 meets the water supply requirement (pH value), and the frequency adjustment value f of the second metering pump 8 satisfies the following first formula:

[0065] In the first formula: f (Hz) is the frequency adjustment value of the second metering pump 8, △C NH3 (mg / L) is the ammonia concentration change required for the condensate in the condensate pipe 2 to meet the water supply requirements (pH value), △Q 凝 (L / h) is the change in the flow rate of the condensate in the condensate pipeline 2, q[(L / h)·(Hz)] is the change in the flow rate of the second metering pump 8 per Hz frequency change, C 计 NH3 (mg / L) is the ammonia concentration value of the ammonia solution in the ammonia liquid measuring tank 3.

[0066] △C NH3 =C 给 NH3 -C 凝 NH3 Thus, it can be further obtained that the frequency adjustment value f of the second metering pump 8 satisfies the following formula:

[0067] Specifically, when the value of f is positive, the absolute value of the frequency f of the second metering pump 8 is increased to increase the discharge flow rate of the second metering pump 8, thereby increasing the ammonia concentration of the feedwater in the feedwater pipeline 5. When the value of f is negative, the absolute value of the frequency f of the second metering pump 8 is decreased to reduce the discharge flow rate of the second metering pump 8, thereby reducing the ammonia concentration of the feedwater in the feedwater pipeline 5. According to the boiler feedwater ammonia addition control method for condensate flow rate fluctuations of the present application, the discharge flow rate of the second metering pump 8 is changed by the condensate flow rate fluctuation. When the condensate flow rate increases, the discharge flow rate of the second metering pump 8 increases; when the condensate flow rate decreases, the discharge flow rate of the second metering pump 8 decreases. The discharge flow rate of the second metering pump 8 is positively correlated with the operating frequency. The specific frequency of the second metering pump 8 can be determined, thereby making the flow rate change of the second metering pump 8 more accurate, thereby facilitating the adjustment of the ammonia concentration and, consequently, the pH value of the feedwater.

[0068] Therefore, the method for controlling the addition of ammonia to boiler feed water when the condensate flow rate varies according to the present application has the advantage of facilitating real-time and accurate adjustment of the pH value of the feed water.

[0069] As shown in Figure 1, in some embodiments, a third ammonia concentration monitor 12 is provided on the feed water pipeline 5. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate varies includes steps S4 and S5.

[0070] In step S4, the third ammonia concentration monitor 12 is used to monitor the ammonia concentration value C of the water in the water supply pipeline 5. 测 NH3 If the ammonia concentration value C monitored by the third ammonia concentration monitor 12 is 测 NH3 The required value C of ammonia concentration in the feed water in the feed water pipe 5 给 NH3 If the difference between is within the first preset range, it is determined that the ammonia concentration in the water supply in the water supply pipeline 5 meets the water supply requirement.

[0071] In step S5, the monitoring data of the third ammonia concentration monitor 12 is used to obtain the pH value of the feed water in the water supply pipeline 5, thereby determining whether the pH value of the feed water meets the requirement.

[0072] In some embodiments, the first ammonia concentration monitor 10 , the second ammonia concentration monitor 11 , and the third ammonia concentration monitor 12 are all conductivity meters.

[0073] There is a calculation relationship between the pH value of the water vapor working medium of the 25°C unit and the conductivity (SC·μS / cm): pH=8.57+lgSC. Therefore, the conductivity of the feed water in the feed water pipeline 5 can be monitored by the third ammonia concentration monitor 12 to obtain the pH value of the feed water.

[0074] The ammonia concentration value and the conductivity value SC in the liquid satisfy the following third formula: C NH3 =(13.2×SC 2 +62.7×SC)×10 -3

[0075] In the third formula: C NH3 is the ammonia concentration in the liquid, and SC is the conductivity of the liquid monitored by the conductivity meter.

[0076] The first ammonia concentration monitor 10 is used to monitor the conductivity of the condensed water in the condensed water pipeline 2. The ammonia concentration of the condensed water in the condensed water pipeline 2 can be determined based on the conductivity of the condensed water in the condensed water pipeline 2. That is, the conductivity value of the condensed water monitored by the first ammonia concentration monitor 10 is substituted into the third formula to obtain the ammonia concentration value C of the condensed water in the condensed water pipeline 2. 凝 NH3 .

[0077] The second ammonia concentration monitor 11 is used to monitor the conductivity of the ammonia solution in the ammonia liquid metering tank 3. The ammonia concentration of the ammonia solution in the ammonia liquid metering tank 3 can be determined based on the conductivity of the ammonia solution in the ammonia liquid metering tank 3. In other words, the conductivity value of the ammonia solution in the ammonia liquid metering tank 3 monitored by the second ammonia concentration monitor 11 is substituted into the third formula to obtain the ammonia concentration value of the ammonia solution in the ammonia liquid metering tank 3.

[0078] As shown in FIG1 , the third ammonia concentration monitor 12 is used to monitor the conductivity of the feed water in the water supply pipeline. The ammonia concentration of the feed water in the water supply pipeline can be determined based on the conductivity of the feed water in the water supply pipeline. Specifically, the conductivity of the feed water in the water supply pipeline 5 monitored by the third ammonia concentration monitor 12 is substituted into the third formula to obtain the ammonia concentration value of the feed water in the water supply pipeline 5.

[0079] In some embodiments, the frequency adjustment value f of the second metering pump 8 is calculated using the following formula:

[0080] The fourth formula: △C NH3 ×△Q 凝 =△Q 计 ×C 计 NH3

[0081] Fifth formula: f=△Q 计 ÷q

[0082] In the fourth and fifth formulas: △Q 计 (L / h) is the flow rate change value of the second metering pump 8. Specifically, the fourth formula can calculate the amount of medicine that needs to be increased or decreased ΔM NH3 (mg / h) The fifth formula is the relationship between the flow rate change value and the frequency change value of the second metering pump 8.

[0083] In some embodiments, a first flow meter 13 is provided on the condensate pipe 2. In step S2, the first flow meter 13 is used to monitor the change value ΔQ of the flow rate of the condensate in the condensate pipe 2. 凝 Specifically, the first flow meter 13 can monitor the flow rate in the condensate pipeline 2 and the flow rate change per unit time.

[0084] In some embodiments, a second flow meter 14 is provided on the ammonia liquid pipeline 4. In step S2, the second flow meter 14 is used to monitor the change value ΔQ of the flow rate of the ammonia solution in the ammonia liquid pipeline 4. 计 Specifically, the second flow meter 14 can monitor the flow rate in the ammonia liquid pipeline 4 and the flow rate change per unit time.

[0085] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0086] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0087] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0088] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0089] In this application, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0090] Although the above embodiments have been shown and described, it is understood that the above embodiments are illustrative and cannot be understood as limitations on the present application. Changes, modifications, substitutions and variations of the above embodiments made by ordinary technicians in this field are all within the scope of protection of the present application.

Claims

1. A method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates, characterized in that: Based on the boiler feed water ammonia addition system, the boiler feed water ammonia addition system includes a condenser, a condensate pipeline, an ammonia liquid pipeline, an ammonia liquid metering tank and a feed water pipeline, the outlet of the condenser is connected to the inlet of the feed water pipeline through the condensate pipeline, the outlet of the ammonia liquid metering tank is connected to the inlet of the feed water pipeline through the ammonia liquid pipeline, the outlet of the feed water pipeline is connected to the water inlet of the boiler, a condensate pump is provided on the condensate pipeline, and a second metering pump is provided on the ammonia liquid pipeline, and the second metering pump is a variable frequency pump; The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate changes comprises the following steps: S1, configure the ammonia concentration in the ammonia liquid metering tank to be C 计 NH3 ammonia solution, determining the flow rate change value q of the second metering pump under each Hz frequency change; S2. Determine the change value ΔQ of the flow rate of the condensate in the condensate pipeline 凝 , determine the ammonia concentration change value △C required for the condensate in the condensate pipeline to meet the water supply requirements NH3 ; S3. Adjust the frequency of the second metering pump so that the ammonia concentration in the water in the water supply pipeline meets the water supply requirements, and the frequency adjustment value f of the second metering pump satisfies the following first formula: In the first formula: f is the frequency adjustment value of the second metering pump, △C NH3 The ammonia concentration change value required for the condensate in the condensate pipeline to meet the water supply requirements, △Q 凝 is the change in the flow rate of the condensate in the condensate pipeline, q is the change in the flow rate of the second metering pump per Hz frequency change, C 计 NH3 is the ammonia concentration value of the ammonia solution in the ammonia liquid metering tank.

2. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates according to claim 1, characterized in that: The condensate pipeline is provided with a first ammonia concentration monitor; In step S1, the ammonia concentration that meets the water supply requirement is C 给 NH3 ; In step S2, the ammonia concentration of the condensed water in the condensed water pipeline is monitored by the first ammonia concentration monitor and the ammonia concentration is C 凝 NH3 , wherein the condensate in the condensate pipeline reaches the required ammonia concentration change value △C to meet the water supply requirements NH3 The following second formula is satisfied: △C NH3 =C 给 NH3 -C 凝 NH3 In the second formula: △C NH3 The ammonia concentration change value required for the condensate in the condensate pipeline to meet the water supply requirements, C 凝 NH3 To monitor the ammonia concentration of the condensate in the condensate pipeline using the first ammonia concentration monitor, C 给 NH3 It is the ammonia concentration value of the water in the water supply pipeline that meets the water supply requirements.

3. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates according to claim 2, characterized in that: The ammonia liquid metering tank is provided with a second ammonia concentration monitor; In step S1, the second ammonia concentration monitor is used to monitor the ammonia concentration of the ammonia solution in the ammonia liquid metering tank, so as to configure the ammonia concentration in the ammonia liquid metering tank to be C 计 NH3 of ammonia solution.

4. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates according to claim 3, characterized in that: A third ammonia concentration monitor is provided on the water supply pipeline; The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate changes includes: S4, using the third ammonia concentration monitor to monitor the ammonia concentration value C of the water in the water supply pipeline 测 NH3 If the ammonia concentration value C monitored by the third ammonia concentration monitor is 测 NH3 The required value C of ammonia concentration in the water supply pipe 给 NH3 If the difference between the two values ​​is within a first preset range, it is determined that the ammonia concentration in the water supply in the water supply pipeline meets the water supply requirement; S5. Utilize the monitoring data of the third ammonia concentration monitor to obtain the pH value of the feed water in the water supply pipeline.

5. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates according to claim 4, characterized in that: The first ammonia concentration monitor, the second ammonia concentration monitor and the third ammonia concentration monitor are all conductivity meters; The first ammonia concentration monitor is used to monitor the conductivity of the condensed water in the condensed water pipeline, and can determine the ammonia concentration of the condensed water in the condensed water pipeline according to the conductivity of the condensed water in the condensed water pipeline; The second ammonia concentration monitor is used to monitor the conductivity of the ammonia solution in the ammonia liquid metering tank, and can determine the ammonia concentration of the ammonia solution in the ammonia liquid metering tank according to the conductivity of the ammonia solution in the ammonia liquid metering tank; The third ammonia concentration monitor is used to monitor the conductivity of the feed water in the water supply pipeline, and can determine the ammonia concentration of the feed water in the water supply pipeline according to the conductivity of the feed water in the water supply pipeline; The ammonia concentration value and the conductivity value SC in the liquid satisfy the following third formula: C NH3 =(13.2×SC 2 +62.7×SC)×10 -3 In the third formula: C NH3 is the ammonia concentration in the liquid, and SC is the conductivity of the liquid monitored by the conductivity meter.

6. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates according to claim 5, characterized in that: The calculation process of the frequency adjustment value f of the second metering pump includes the following formula: The fourth formula: △C NH3 ×△Q 凝 =△Q 计 ×C 计 NH3 The fifth formula: f=△Q 计 ÷q In the fourth and fifth formulas: △Q 计 is the discharge flow rate change value of the second metering pump.

7. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates according to claim 6, characterized in that: A first flow meter is provided on the condensate pipeline; In step S2, the first flow meter is used to monitor the change in the flow rate of the condensate in the condensate pipeline. Value △Q 凝 ; A second flow meter is provided on the ammonia liquid pipeline; In step S2, the second flow meter is used to monitor the change value ΔQ of the flow rate of the ammonia solution in the ammonia solution pipeline. 计 .

8. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate varies according to any one of claims 1 to 7, characterized in that: The boiler feed water ammonia addition system includes a deaerator, wherein the inlet of the deaerator is connected to the outlet of the water supply pipeline; A fourth pipeline, the inlet of the fourth pipeline is connected to the outlet of the deaerator, a third pump body is provided on the fourth pipeline, and the outlet of the fourth pipeline is connected to the water inlet of the boiler.

9. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates according to claim 8, characterized in that: The boiler feed water ammonia addition system includes a first heater, the first heater being arranged on the water supply pipeline; A second heater is provided on the fourth pipeline.

10. The method for controlling the addition of ammonia to boiler feed water when the condensate flow rate fluctuates according to claim 8, characterized in that: The condensate pipeline includes a first branch and a second branch connected in parallel, a valve is provided on the first branch, and a fine treatment device is provided on the second branch.

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