阅读说明：本技术 一种锅炉给水pH自动控制装置及控制方法 (Automatic control device and control method for boiler feed water pH ) 是由 谢宙桦 黄万启 张洪博 黄善锋 刘涛 张瑞 齐超 刘铁勇 于 2021-08-31 设计创作，主要内容包括：本发明公开了一种锅炉给水pH自动控制装置及控制方法,装置包括：氨水罐、凝结水加氨计量泵、PLC控制器和省煤器入口电导率在线仪表；所述氨水罐通过管道连通凝结水泵出口的第一管道加氨点,管道上设置有凝结水加氨计量泵；与锅炉给水系统的省煤器入口连通的第二管路上设置省煤器入口电导率在线仪表；PLC控制器电连接凝结水加氨计量泵、省煤器入口电导率在线仪表。该装置控制省煤器入口电导率的达到稳定,即满足锅炉给水pH的控制要求。(The invention discloses a boiler feed water pH automatic control device and a control method, wherein the device comprises: the system comprises an ammonia water tank, a condensed water ammonia adding metering pump, a PLC (programmable logic controller) and an economizer inlet conductivity online instrument; the ammonia water tank is communicated with a first pipeline ammoniation point at the outlet of the condensate pump through a pipeline, and a condensate ammoniation metering pump is arranged on the pipeline; a second pipeline communicated with an economizer inlet of the boiler water supply system is provided with an economizer inlet conductivity online instrument; the PLC is electrically connected with the condensed water ammonia adding metering pump and the economizer inlet conductivity online instrument. The device controls the conductivity of the coal economizer inlet to be stable, namely, the control requirement of the pH value of the boiler feed water is met.)

1. The utility model provides a boiler feedwater pH automatic control device which characterized in that includes: the system comprises an ammonia water tank (1), a condensed water ammonia adding metering pump (3), a PLC (programmable logic controller) controller (6) and an economizer inlet conductivity online instrument (7);

the ammonia water tank (1) is communicated with a first pipeline ammonia adding point at the outlet of the condensate pump through a pipeline, and a condensate water ammonia adding metering pump (3) is arranged on the pipeline; a second pipeline communicated with an economizer inlet of the boiler water supply system is provided with an economizer inlet conductivity online instrument (7); the PLC (6) is electrically connected with the condensed water ammonia adding metering pump (3) and the economizer inlet conductivity online instrument (7).

2. The automatic control device for the pH of boiler feed water according to claim 1,

and the pipelines at the inlet and the outlet of the condensed water ammonia adding metering pump (3) are respectively provided with a condensed water ammonia adding metering pump inlet ball valve (2) and a condensed water ammonia adding metering pump outlet ball valve (4).

3. The automatic control device for the pH of boiler feed water according to claim 1,

the PLC controller (6) is connected with the touch display screen (5).

4. The automatic control device for the pH of boiler feed water according to claim 1,

the economizer inlet conductivity online instrument (7) is communicated with the second pipeline through a measuring pipeline, and an outlet of the measuring pipeline is led into the recovery tank.

5. The control method of the boiler feed water pH automatic control device according to any one of claims 1 to 4, characterized by comprising the steps of:

the PLC acquires the conductivity value of the inlet of the economizer according to the online meter (7) of the conductivity of the inlet of the economizer, and controls the starting or the closing of the condensed water ammonia dosing pump (3) according to the difference value between the set conductivity value and the actual conductivity value, thereby controlling the pH value of the feed water.

6. The control method of the boiler feed water pH automatic control device according to claim 5, characterized by comprising:

setting a conductivity set value of an economizer inlet in a PLC (programmable logic controller), and setting PI initial parameters, wherein the PI initial parameters comprise a proportional coefficient and an integral coefficient; after a real-time signal is collected by the economizer inlet conductivity meter, the real-time signal is compared with a set economizer inlet conductivity value and input into a RBF-PI control method to obtain the control frequency of the condensed water ammonia dosing metering pump (3); and simultaneously inputting the difference e (k-1) between the conductivity of the economizer inlet at the previous moment and a set value and the difference e (k) at the moment into an RBF-PI control method, dynamically optimizing PI control parameters to ensure that the RBF-PI controller is dynamically optimized, ensuring that the conductivity of the economizer inlet reaches a desired value, and controlling the pH value of the boiler feed water.

7. The control method of the boiler feed water pH automatic control device according to claim 5, characterized by comprising:

setting a conductivity set value of an economizer inlet in a PLC (programmable logic controller), and setting PI initial parameters, wherein the PI initial parameters comprise a proportional coefficient and an integral coefficient; after a real-time signal is collected by the economizer inlet conductivity meter, the real-time signal is compared with a set economizer inlet conductivity value and input into a RBF-PI control method to obtain the control frequency of the condensed water ammonia dosing metering pump (3); and simultaneously inputting the difference e (k-1) between the conductivity of the economizer inlet at the previous moment and a set value and the difference e (k) at the moment into an RBF-PI control method, dynamically optimizing PI control parameters to ensure that the RBF-PI controller is dynamically optimized, ensuring that the conductivity of the economizer inlet reaches a desired value, and controlling the pH value of the boiler feed water.

8. The control method of the boiler feed water pH automatic control device according to claim 6, characterized by comprising:

let k be the system control error

e(k)＝rin(k)-y(k)

The PI controller adopts an incremental algorithm, and two inputs of the PI controller are

Setting a performance index function of a PI controller to be

K is obtained by gradient descent_p,K_iIs adjusted by an amount of

In the formula eta_p,η_i-the learning rates representing proportional and integral, respectively;jacobian information, i.e. the sensitivity function of the output of the controlled object to the control input, is expressed by

The output of the PI controller is

u(k)＝u(k-1)+K_px₁(k)+K_ix₂(k)

Wherein rin (k) isSet value, K_pIs a proportionality coefficient, K_iAnd u (k) is an integral coefficient, and u (k) is a control quantity, namely a condensed water and ammonia adding pump frequency command.

Technical Field

The invention relates to the technical field of boiler feed water pH ammoniation control, in particular to a boiler feed water pH automatic control device and a control method.

Background

The pH control of boiler feed water is an important part in a chemical system of a power plant, and the pH value of the feed water is improved by adding ammonia water into a feed water pipeline, so that the method is the most economical and practical method for preventing the feed water from corroding metals. The pH value of the boiler feed water and the conductivity of the boiler feed water have a corresponding linear relation, namely pH is 8.57+ lgSC, the conductivity with high reliability can be used as an index, and the corrosion of the metal of the feed water pipeline can be effectively prevented and controlled by controlling the stability of the conductivity of the feed water.

At present, two points of ammonia adding are carried out on feed water by a power plant through a condensate mother pipe outlet and a deaerator outlet, the two points of ammonia adding are both manually operated, the frequency of an ammonia adding pump is modified by simply depending on the pH index of the feed water through manual adjustment, and the pH water quality index of the feed water is unstable due to the mutual disturbance of the two points of ammonia adding and overlarge hysteresis of the pH index, so that a boiler feed water pipeline has certain equipment corrosion risk.

Because most thermal power plants have the working conditions of peak shaving operation and load fluctuation, the requirement of the working condition of load fluctuation cannot be met by manually adjusting the ammonia adding amount, the pH value of feed water is unstable, the safety of unit operation is reduced, and the difficulty of operating personnel for operating the ammonia adding metering pump is increased. In view of the above, an automatic control device and method for the pH of boiler feed water are needed.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides the automatic control device and the control method for the pH of the boiler feed water.

In order to achieve the purpose, the invention adopts the following technical scheme:

an automatic control device for the pH of boiler feed water comprises: the system comprises an ammonia water tank, a condensed water ammonia adding metering pump, a PLC (programmable logic controller) and an economizer inlet conductivity online instrument;

the ammonia water tank is communicated with a first pipeline ammoniation point at the outlet of the condensate pump through a pipeline, and a condensate ammoniation metering pump is arranged on the pipeline; a second pipeline communicated with an economizer inlet of the boiler water supply system is provided with an economizer inlet conductivity online instrument; the PLC is electrically connected with the condensed water ammonia adding metering pump and the economizer inlet conductivity online instrument.

As a further improvement of the invention, the pipelines of the inlet and the outlet of the condensed water ammonia adding metering pump are respectively provided with a condensed water ammonia adding metering pump inlet ball valve and a condensed water ammonia adding metering pump outlet ball valve.

As a further improvement of the invention, the PLC is connected with a touch display screen.

As a further improvement of the invention, the economizer inlet conductivity online instrument is communicated with the second pipeline through a measuring pipeline, and the outlet of the measuring pipeline is introduced into the recovery tank.

A control method of a boiler feed water pH automatic control device comprises the following steps:

the PLC acquires the conductivity value of the inlet of the economizer according to the online meter of the conductivity of the inlet of the economizer, and controls the starting or the closing of the condensed water ammonia dosing pump according to the difference value between the set conductivity value and the actual conductivity value, thereby controlling the pH value of the feed water.

As a further improvement of the present invention, specifically, the present invention includes:

setting a conductivity set value of an economizer inlet in a PLC (programmable logic controller), and setting PI initial parameters, wherein the PI initial parameters comprise a proportional coefficient and an integral coefficient; after a real-time signal is collected by the conductivity meter at the inlet of the economizer, the real-time signal is compared with a set conductivity value at the inlet of the economizer and is input into a RBF-PI control method to obtain the control frequency of the condensed water ammonia adding metering pump; and simultaneously inputting the difference e (k-1) between the conductivity of the economizer inlet at the previous moment and a set value and the difference e (k) at the moment into an RBF-PI control method, dynamically optimizing PI control parameters to ensure that the RBF-PI controller is dynamically optimized, ensuring that the conductivity of the economizer inlet reaches a desired value, and controlling the pH value of the boiler feed water.

As a further improvement of the invention, the method specifically comprises the following steps:

let k be the system control error

e(k)＝rin(k)-y(k)

The PI controller adopts an incremental algorithm, and two inputs of the PI controller are

Setting a performance index function of a PI controller to be

K is obtained by gradient descent_p,K_iIs adjusted by an amount of

In the formula eta_p,η_i-the learning rates representing proportional and integral, respectively;jacobian information, i.e. the sensitivity function of the output of the controlled object to the control input, is expressed by

Based on the above process, the output of the PI controller is

u(k)＝u(k-1)+K_px₁(k)+K_ix₂(k)

Wherein rin (K) is a set value, K_pIs a proportionality coefficient, K_iIs an integral coefficient, u (k) is a control quantityAnd adding ammonia into the condensed water and giving a pump frequency instruction.

Compared with the prior art, the invention has the following advantages:

the device of the invention adds ammonia water to a boiler water supply pipeline by using a condensed water and ammonia adding metering pump at the outlet of the condensed water pump. The sampling part is designed to increase an online conductivity meter at the inlet of the economizer to perform online conductivity measurement on boiler feed water, and the device does not need to set a large number of parameters when external factors change, is convenient for operation of operators and ensures the stability of the pH value of the boiler feed water.

Further, the pH value is converted to the feed water pH value by the formula pH 8.57+ lgSC. The PLC controller uses the RBF-PI algorithm, so that the hysteresis of the boiler feed water ammonia adding system is reduced, the PI parameters do not need to be manually adjusted, the RBF-PI algorithm can dynamically adjust the PI parameters according to historical data, the frequency of the condensed water ammonia adding metering pump is dynamically changed, and the ammonia adding amount of the boiler feed water is accurately changed when the working condition of the boiler feed water system changes. The device is simple and practical and the conductivity accuracy of control boiler feedwater is high to guarantee the stability of boiler feedwater pH value, satisfy the requirement of boiler feedwater pH.

The method solves the control problem of large lag of boiler water feeding and ammonia adding, uses RBF-PI control algorithm used in the PLC controller, uses the difference values e (k-1) and e (k) of the actual value and the expected value of the electric conductivity at the previous sampling moment and the current moment as the input end of the RBF of the neural network, dynamically modifies the parameters of the PI controller through the calculation of the RBF of the neural network, including the proportionality coefficient P and the integral coefficient I, thereby obtaining the optimal output value of the RBF-PID controller, acting on the frequency of the condensed water ammonia adding metering pump, reducing the workload of operators, and ensuring the safety and the economy of the operation of a generator set.

Drawings

FIG. 1 is a diagram of an automatic control device for the pH of boiler feed water;

FIG. 2 shows a RBF-PI control method for the boiler feed water pH automatic control device.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, the automatic control device for the pH of boiler feed water comprises: the system comprises a first pipeline communicated with a condensate water main pipe of a boiler water supply system, a second pipeline communicated with an economizer inlet of the boiler water supply system, an ammonia water tank 1, a condensate water ammonia adding metering pump 3, a PLC (programmable logic controller) 6 and an economizer inlet conductivity online instrument 7;

the bottom of the ammonia tank 1 is communicated with a pipeline ammonia adding point of an outlet of the condensate pump through a pipeline, a condensate ammonia adding metering pump 3 is arranged on the pipeline, and an inlet ball valve 2 of the condensate ammonia adding metering pump and an outlet ball valve 4 of the condensate ammonia adding metering pump are respectively arranged on the pipelines of an inlet and an outlet of the condensate ammonia adding metering pump 3; a pipeline communicated with an economizer inlet of a boiler water supply system is provided with an economizer inlet conductivity online instrument 7; the PLC 6 is connected with the condensed water ammonia adding metering pump 3 and the economizer inlet conductivity online instrument 7.

The PLC controller 6 is connected to a touch display screen 5, which can be used for inputting data and displaying data. The device is equipped with input device, such as mouse and keyboard, or touch display screen.

As a preferred embodiment, the PLC acquires the conductivity value of the inlet of the economizer according to the online meter 7 of the conductivity of the inlet of the economizer, and controls the starting or the closing of the condensed water ammonia dosing pump 3 according to the difference value between the set conductivity value and the actual conductivity value. The PLC controller controls the operation only by comparing with a set value. The method can be realized by only the basic functions of the PLC controller without adopting complex algorithms.

Preferably, in order to realize accurate control, the PLC controller comprises an RBF-PI control module, the RBF-PI control module is used for controlling the conductivity value of the inlet of the economizer, and the conductivity of the inlet of the economizer is ensured to reach a desired value through a rolling optimized PI control parameter according to a difference value between a set conductivity value and an actual conductivity value, so that the pH value of feed water is controlled.

A RBF-PI control method of a boiler feed water pH automatic control device comprises the following steps:

and setting a conductivity set value of the coal economizer inlet on the touch screen 5, and setting PI initial parameters, wherein the PI initial parameters comprise a proportional coefficient and an integral coefficient. And after a real-time signal is collected by the conductivity meter at the inlet of the economizer, the real-time signal is compared with a set conductivity value at the inlet of the economizer and is input into an RBF-PI control method to obtain the control frequency of the condensed water ammonia addition metering pump 3, and meanwhile, a difference value e (k-1) between the conductivity of the inlet of the economizer at the previous moment and the set conductivity value and a difference value e (k) at the moment are input into the RBF-PI control method to dynamically optimize PI control parameters, ensure that the dynamic optimization of the RBF-PI controller is realized, ensure that the conductivity of the inlet of the economizer reaches a desired value, and further control the pH value of the feed water of the boiler.

The RBF-PI control algorithm is implemented using STL language of Siemens SMART S7-200 PLC controller.

The structure block diagram of the RBF-PI control algorithm is shown in FIG. 2. Gradient information is acquired by utilizing RBF neural network online identification, and parameters of the PI controller are adjusted in an online self-adaptive manner based on the gradient information, so that the purpose of further improving the control performance of the system is achieved.

Let k be the system control error

e(k)＝rin(k)-y(k)

The PI controller adopts an incremental algorithm, and two inputs of the PI controller are

Setting a performance index function of a PI controller to be

K is obtained by gradient descent_p,K_iIs adjusted by an amount of

In the formula eta_p,η_i-the learning rates representing proportional and integral, respectively;jacobian information, i.e. the sensitivity function of the output of the controlled object to the control input, can be expressed by

Based on the above process, the output of the PI controller is

u(k)＝u(k-1)+K_px₁(k)+K_ix₂(k)

Wherein rin (K) is a set value, K_pIs a proportionality coefficient, K_iAnd u (k) is an integral coefficient, and u (k) is a control quantity, namely a condensed water and ammonia adding pump frequency command.

The following description will further describe an embodiment of the present invention with reference to fig. 1 and 2.

Examples

As shown in the attached figure 1, when the automatic control device for the boiler feed water pH is put into operation, the inlet ball valve 2 of the condensate ammonia adding metering pump and the outlet ball valve 4 of the condensate ammonia adding pump are opened, the condensate ammonia adding metering pump 3 is started after the set value of the conductivity of the coal economizer inlet is arranged on the touch screen 5, and the automatic control device for the boiler feed water pH can be put into operation automatically by clicking an automatic button.

As shown in FIG. 2, in order to realize accurate dynamic control, the invention provides a preferred embodiment, and an RBF-PI initial parameter K is set_pIs a proportionality coefficient, K_iDynamically optimizing K for an integral coefficient according to the conductivity error e (K-1) acquired in real time and the difference e (K) at the moment_pIs a proportionality coefficient, K_iAnd (3) calculating the frequency of the condensed water ammonia adding metering pump at the same time to obtain an integral coefficient, so that the conductivity of the inlet of the economizer reaches a set value, and the control requirement of the pH value of the boiler feed water is met.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.