An automatic ammonia addition control system for multiple factors in a power plant and its control method

Abstract

An automatic ammonia addition control system and its control method for multiple factors in a power plant. The system includes an automatic ammonia addition control cabinet, an ammonia addition tank, an ammonia addition metering pump, a water system concentration meter or a conductivity meter. The PLC in the automatic ammonia addition control cabinet collects the water system flow rate, uses the judgment block in the PLC to judge the flow rate section where the current water system flow rate is located, and then gives the initial feedforward frequency. The operator manually inputs the current stroke of the ammonia addition metering pump and the set value of the water system concentration or conductivity on the human-machine interface. After the PLC collects the concentration or conductivity of the ammonia addition tank, the stroke of the ammonia addition metering pump, and the set value of the water system concentration or conductivity, it calculates the multi-factor coefficient. The PLC collects the current value of the water system concentration or conductivity and calculates the PID output frequency. The present invention overcomes the influence of multiple factors such as changes in the water system flow rate, changes in the concentration or conductivity of the ammonia addition tank, changes in the stroke of the metering pump, and changes in the set value of the water system concentration or conductivity in the power plant, and realizes the automatic and precise control of ammonia addition to the water system.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia addition in the water system of power plants, and particularly relates to an automatic ammonia addition control system for multiple factors in a power plant and a control method thereof. Background Art

[0002] The control method of ammonia addition in the water system of power plants is mainly that operators manually adjust the frequency of the ammonia addition metering pump according to the changes in the water system flow rate, the water system concentration or the conductivity. This not only causes a huge workload for the operators, but also causes large fluctuations in the water system concentration or conductivity. If the water system concentration or conductivity is too low, it will cause corrosion of the thermal equipment in the power plant. If the conductivity is too high, it will cause waste of ammonia addition or a short operation cycle of the polishing treatment.

[0003] Currently, the common automatic ammonia addition control method only adjusts through the PID control algorithm using the water system concentration or conductivity signal. Since the ammonia addition system in the water system belongs to a "large lag" system, it usually takes 15 minutes for the change in the water system flow rate or the frequency of the ammonia addition metering pump to cause a change in the water system concentration or conductivity. It cannot be adjusted only through the PID control algorithm, and the fluctuation range of the water system concentration or conductivity in this automatic ammonia addition is equivalent to that of the manual ammonia addition method. Moreover, when the concentration of the ammonia addition tank, the stroke of the ammonia addition metering pump, and the set value of the water system concentration or conductivity change, the control difficulty of the automatic ammonia addition is greater. Summary of the Invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an automatic ammonia addition control system for multiple factors in a power plant and a control method thereof. This system can overcome the influence of multiple factors such as the change in the water system flow rate of the power plant, the change in the concentration or conductivity of the ammonia addition tank, the change in the stroke of the metering pump, and the change in the set value of the water system concentration or conductivity, and realize the precise automatic control of ammonia addition in the water system.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] An automatic ammonia addition control system for multiple factors in a power plant includes a water system concentration meter or conductivity meter 4 arranged on the pipeline of the water system of the power plant, an ammonia addition tank 2 communicated with the pipeline of the water system of the power plant, and an ammonia addition metering pump 3 arranged on the pipeline connecting the ammonia addition tank 2 and the pipeline of the water system of the power plant; the ammonia addition tank 2 includes a medicine tank 2-1 and a concentration meter or conductivity meter 2-2 arranged in the medicine tank 2-1; it also includes an automatic ammonia addition control cabinet 1, and the automatic ammonia addition control cabinet 1 includes a control cabinet body 1-1, a PLC 1-2 installed in the control cabinet body 1-1, and a human-machine interface 1-3 connected to the PLC 1-2; the PLC 1-2 is connected to the water system concentration meter or conductivity meter 4, the concentration meter or conductivity meter 2-2, and the ammonia addition metering pump 3.

[0007] The automatic ammonia addition control method of the automatic ammonia addition control system for multiple factors in a power plant. The operator manually inputs the current stroke of the ammonia addition metering pump and the set value of the concentration or conductivity of the water system on the man-machine interface 1-3. PLC1-2 collects the flow rate of the power plant water system, the current concentration or conductivity of the ammonia addition tank, the current stroke of the ammonia addition metering pump, the set value of the concentration or conductivity of the power plant water system, and the current value of the concentration or conductivity of the power plant water system. Through the automatic ammonia addition mathematical control model, PLC1-2 gives the frequency of the ammonia addition metering pump in real time, and finally realizes the automatic control of ammonia addition; the current concentration or conductivity of the ammonia addition tank is measured by the concentration meter or conductivity meter 2-2 set in the medicine tank 2-1, and the current value of the concentration or conductivity of the power plant water system is measured by the water system concentration meter or conductivity meter 4 set on the pipeline of the power plant water system.

[0008] The automatic ammonia addition mathematical control model is: frequency of ammonia addition metering pump = initial feedforward frequency × multi-factor coefficient + PID output frequency.

[0009] For the described initial feedforward frequency, the 0-100% of the water system flow rate is divided into several flow rate segments. PLC1-2 in the automatic ammonia addition control cabinet 1 collects the flow rate of the power plant water system, uses the judgment block in PLC1-2 to judge the flow rate segment where the current water system flow rate is located, and then gives the corresponding initial feedforward frequency; the water system flow rate segments and the initial feedforward frequencies are listed in Table 1;

[0010] Table 1 Water system flow rate segments and corresponding initial feedforward frequencies

[0011] Water system flow segmentation Initial feedforward frequency unit: Hz 0～30％ 10 30％～35％ 11.5 35％～40％ 13.0 40％～45％ 14.4 45％～50％ 15.8 50％～55％ 17.1 55％～60％ 18.4 60％～65％ 19.6 65％～70％ 20.8 70％～75％ 21.9 75％～80％ 23.0 80％～85％ 24.0 85％～90％ 25.0 90％～95％ 25.9 95％～100％ 26.8

[0012] For the described multi-factor coefficient, the multi-factor coefficient

[0013] = 1×(c a / c b )×(M a / M b )×(c d / c c ) = 1×((13.2S a 2 + 62.7S a ) / (13.2S b 2 + 62.7S b ))×(M a / M b )×((13.2S d 2 + 62.7S d ) / (13.2S c 2 + 62.7Sc ), where c a is the initial concentration of ammonia water in the ammonia addition tank, and c b is the current concentration of ammonia water in the ammonia addition tank, and c c is the initial set concentration of ammonia water in the water system, and c d is the current set concentration of ammonia water in the water system, and the units are all mg / L; S a is the initial conductivity of ammonia water in the ammonia addition tank, and S b is the current conductivity of ammonia water in the ammonia addition tank, and S c is the initial set value of the water system conductivity, and S d is the current set value of the water system conductivity, and the units are all μS / cm; M a is the initial stroke of the ammonia addition metering pump, and M b is the current stroke of the ammonia addition metering pump, and the unit is %.

[0014] The PID output frequency described above is characterized in that: the PLC1-2 in the automatic ammonia addition control cabinet 1 collects the current value of the concentration or conductivity of the power plant water system, and gives the PID output frequency through the PID control algorithm in the PLC. Among them, P is the proportional gain, with a value of 1.2; I is the integral time, with a value of 80, and the unit is seconds; D is the differential time, with a value of 5, and the unit is seconds.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1) Compared with manual ammonia addition. It realizes the full-automatic control of ammonia addition in the water system, and does not require the operator to manually adjust the frequency of the ammonia addition metering pump according to the changes in the water system flow rate, water system concentration or conductivity. Moreover, the accuracy of the water system concentration or conductivity during manual ammonia addition is usually within ±20% of the target value, and the accuracy of multi-factor automatic ammonia addition can reach within ±5% of the target value.

[0017] 2) Compared with the usual automatic ammonia addition. It takes into account multiple factors that affect the automatic ammonia addition effect, such as the water system flow rate, the concentration of the ammonia addition tank, the stroke of the ammonia addition metering pump, and the set value of the water system concentration or conductivity. It overcomes the change in the water system flow rate through feedforward, and overcomes the changes in the concentration or conductivity of the ammonia addition tank, the stroke of the ammonia addition metering pump, and the set value of the water system concentration or conductivity through the multi-factor coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the overall structure of the system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Such as Figure 1As shown in the figure, an automatic ammonia addition control system for multiple factors in a power plant according to the present invention includes a water system concentration meter or conductivity meter 4 provided on the pipeline of the water system in the power plant, an ammonia addition tank 2 communicated with the pipeline of the water system in the power plant, and an ammonia addition metering pump 3 provided on the pipeline connecting the ammonia addition tank 2 and the pipeline of the water system in the power plant; the ammonia addition tank 2 includes a medicine tank 2-1 and a concentration meter or conductivity meter 2-2 provided in the medicine tank 2-1; it further includes an automatic ammonia addition control cabinet 1, and the automatic ammonia addition control cabinet 1 includes a control cabinet body 1-1, a PLC 1-2 installed in the control cabinet body 1-1, and a human-machine interface 1-3 connected to the PLC 1-2; the PLC 1-2 is connected to the water system concentration meter or conductivity meter 4, the concentration meter or conductivity meter 2-2, and the ammonia addition metering pump 3.

[0021] For the automatic ammonia addition control method of the automatic ammonia addition control system for multiple factors in a power plant according to the present invention, the operator manually inputs the current stroke of the ammonia addition metering pump and the set value of the water system concentration or conductivity on the human-machine interface 1-3. The PLC 1-2 collects the flow rate of the water system in the power plant, the current concentration or conductivity of the ammonia addition tank, the current stroke of the ammonia addition metering pump, the set value of the water system concentration or conductivity in the power plant, and the current value of the water system concentration or conductivity in the power plant. Through the automatic ammonia addition mathematical control model, the PLC 1-2 gives the frequency of the ammonia addition metering pump in real time, and finally realizes the automatic control of ammonia addition. The current concentration or conductivity of the ammonia addition tank is measured by the conductivity meter 2-2 provided in the medicine tank 2-1, and the current value of the water system concentration or conductivity in the power plant is measured by the water system concentration meter or conductivity meter 4 provided on the water system pipeline.

[0022] The automatic ammonia addition mathematical control model is: the frequency of the ammonia addition metering pump = the initial feedforward frequency × the multi-factor coefficient + the PID output frequency.

[0023] For the described initial feedforward frequency, the 0-100% of the water system flow rate is divided into several flow rate segments. The PLC 1-2 in the automatic ammonia addition control cabinet 1 collects the flow rate of the water system in the power plant, and uses the judgment block in the PLC 1-2 to judge the flow rate segment where the current water system flow rate is located, and then gives the corresponding initial feedforward frequency. The water system flow rate segments and the initial feedforward frequencies in the power plant are listed in Table 1.

[0024] Table 1 Water system flow rate segments and corresponding initial feedforward frequencies

[0025]

[0026]

[0027] For the described multi-factor coefficient, the multi-factor coefficient

[0028] = 1×(c a / c b)×(M a / M b )×(c d / c c )=1×((13.2S a 2 +62.7S a ) / (13.2S b 2 +62.7S b ))×(M a / M b )×( (13.2S d 2 +62.7S d ) / (13.2S c 2 +62.7S c ))), where c a is the initial concentration of ammonia water in the ammonia addition tank, c b is the current concentration of ammonia water in the ammonia addition tank, c c is the initial set concentration of ammonia water in the water system, c d is the current set concentration of ammonia water in the water system, and the unit is mg / L; S a is the initial conductivity of ammonia water in the ammonia addition tank, S b is the current conductivity of ammonia water in the ammonia addition tank, S c is the initial set value of the conductivity of the water system, S d is the current set value of the conductivity of the water system, and the unit is μS / cm; M a is the initial stroke of the ammonia addition metering pump, M b is the current stroke of the ammonia addition metering pump, and the unit is %.

[0029] Regarding the PID output frequency, the PLC1-2 in the automatic ammonia addition control cabinet 1 collects the current value of the concentration or conductivity of the power plant water system, and gives the PID output frequency through the PID control algorithm in the PLC. Among them, P is the proportional gain, with a value of 1.2; I is the integral time, with a value of 80, and the unit is seconds; D is the differential time, with a value of 5, and the unit is seconds.

Claims

1. An automatic ammonia addition control method for a multi-factor automatic ammonia addition control system in a power plant, characterized in that: The automatic ammonia addition control system includes a water system densitometer or conductivity meter (4) installed on the pipeline of the power plant water system, an ammonia addition tank (2) communicated with the pipeline of the power plant water system, and an ammonia addition metering pump (3) arranged on the pipeline where the ammonia addition tank (2) is communicated with the pipeline of the power plant water system; the ammonia addition tank (2) includes a medicine tank (2-1) and a conductivity meter (2-2) arranged in the medicine tank (2-1); it also includes an automatic ammonia addition control cabinet (1), and the automatic ammonia addition control cabinet (1) includes a control cabinet body (1-1), a PLC (1-2) installed in the control cabinet body (1-1), and a human-machine interface (1-3) connected to the PLC (1-2); the PLC (1-2) is connected to the water system densitometer or conductivity meter (4), the conductivity meter (2-2) and the ammonia addition metering pump (3). The automatic ammonia addition control method is as follows: The operator manually inputs the current stroke of the ammonia addition metering pump and the set value of the water system density or conductivity on the human-machine interface (1-3). The PLC (1-2) collects the flow rate of the power plant water system, the current density or conductivity of the ammonia addition tank, the current stroke of the ammonia addition metering pump, the set value of the density or conductivity of the power plant water system, and the current value of the density or conductivity of the power plant water system. Through the automatic ammonia addition mathematical control model, the PLC (1-2) gives the frequency of the ammonia addition metering pump in real time, and finally realizes the automatic control of ammonia addition; the current density or conductivity of the ammonia addition tank is measured by the conductivity meter (2-2) arranged in the medicine tank (2-1), and the current value of the density or conductivity of the power plant water system is measured by the water system densitometer or conductivity meter (4) arranged on the pipeline of the power plant water system. The automatic ammonia addition mathematical control model is: ammonia addition metering pump frequency = initial feedforward frequency × multi-factor coefficient + PID output frequency. For the described initial feedforward frequency, the 0 - 100% of the flow rate of the power plant water system is divided into several flow rate segments. The PLC (1 - 2) in the automatic ammonia addition control cabinet (1) collects the flow rate of the power plant water system, uses the judgment block in the PLC (1 - 2) to judge the flow rate segment where the current water system flow rate is located, and then gives the corresponding initial feedforward frequency; when the flow rate of the power plant water system is between 0 - 30%, the corresponding initial feedforward frequency is 10 Hz; when the flow rate of the power plant water system is between 30 - 35%, the corresponding initial feedforward frequency is 11.5 Hz; when the flow rate of the power plant water system is between 35 - 40%, the corresponding initial feedforward frequency is 13.0 Hz; when the flow rate of the power plant water system is between 40 - 45%, the corresponding initial feedforward frequency is 14.4 Hz; when the flow rate of the power plant water system is between 45 - 50%, the corresponding initial feedforward frequency is 15.8 Hz; when the flow rate of the power plant water system is between 50 - 55%, the corresponding initial feedforward frequency is 17.1 Hz; when the flow rate of the power plant water system is between 55 - 60%, the corresponding initial feedforward frequency is 18.4 Hz; when the flow rate of the power plant water system is between 60 - 65%, the corresponding initial feedforward frequency is 19.6 Hz; when the flow rate of the power plant water system is between 65 - 70%, the corresponding initial feedforward frequency is 20.8 Hz; when the flow rate of the power plant water system is between 70 - 75%, the corresponding initial feedforward frequency is 21.9 Hz; when the flow rate of the power plant water system is between 75 - 80%, the corresponding initial feedforward frequency is 23.0 Hz; when the flow rate of the power plant water system is between 80 - 85%, the corresponding initial feedforward frequency is 24.0 Hz; when the flow rate of the power plant water system is between 85 - 90%, the corresponding initial feedforward frequency is 25.0 Hz; when the flow rate of the power plant water system is between 90 - 95%, the corresponding initial feedforward frequency is 25.9 Hz; when the flow rate of the power plant water system is between 95 - 100%, the corresponding initial feedforward frequency is 26.8 Hz; The multi-factor coefficient, multi-factor coefficient = 1×(c a / c b )×(M a / M b )×(c d / c c ) = 1×((13.2S a 2 +62.7S a ) / (13.2S b 2 +62.7S b ))×(M a / M b )×((13.2S d 2 +62.7S d ) / (13.2S c 2 +62.7S c ))), where c a is the initial concentration of ammonia water in the ammonia addition tank, c b is the current concentration of ammonia water in the ammonia addition tank, c c is the initial set concentration of ammonia water in the water system, c d is the current set concentration of ammonia water in the water system, and the unit is mg / L; S a is the initial conductivity of ammonia water in the ammonia addition tank, S b is the current conductivity of ammonia water in the ammonia addition tank, S c is the initial set value of the water system conductivity, S d is the current set value of the water system conductivity, and the unit is μS / cm; M a is the initial stroke of the ammonia addition metering pump, M b is the current stroke of the ammonia addition metering pump, and the unit is %.

2. The automatic ammonia addition control method of the automatic ammonia addition control system for multiple factors in a power plant according to claim 1, characterized in that: For the described PID output frequency, the PLC (1 - 2) in the automatic ammonia addition control cabinet (1) collects the current value of the concentration or conductivity of the power plant water system, and gives the PID output frequency through the PID control algorithm in the PLC; among them, P is the proportional gain, with a value of 1.2; I is the integral time, with a value of 80, and the unit is seconds; D is the derivative time, with a value of 5, and the unit is seconds.

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